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iSTRONOGRAPHY, 






ASTRONOMICAL GEOGRAPHY, 



WITH THE USE OF THE GLOBES. 



rrnT ix 

CLASSES, OR FUR - HBTBOU. 



BY KM MA WILL A Ilk 



4 i^. 



TEOT, \. V.: 

MERRIAM, Mo 00. 

1854. 



Entered according to Act of Congress, in the year 1854, 

By MERRIAM, MOORE &CO., 

In the Clerk's Office of the District Conrt for the Northern District of 
New York. 



1 1 



TO 



CHARLES DAVIES, ESQ., 

THE FRIEM D THE MATH KMATK AL EDUCATOR 

IT, 

il Ovilork is kstribrb, 

IS TORE* OF AMOBJ ; KR LABORS 

in i ■ m \n ncn 

Or ESTEEM FOR HVJ VIRTUES, 

A5D OF THE SACRED RRXZMBRAN< ■ Of KAMI YEARS OF 

1 1 II* ; 

I.V 

J.MMA WILLARD 



PREFACE. 



fdi I requested by the "Publisher of 

this WOck, to write for him | small volume to nceom- 
pany and explain the Globes, she undertook the ta>k with 
pleasure; having, in the long course of her duties ej IVinci- 
pal of the Troy Female Seminary, felt the need of new aids in 
fully understanding them; and she had long entertained the 
opinion, that a radical error was committed in elementary 
works on Astronomy M d with Geography, Id put- 

ting d«»wn the definitions of the Horizon. Zenith, and other 
positions depc I fteorror, as some- 

thing of the same kind, as the Equator and Pi iaj 1 4 the Earth, 
and all those definition*, which refer to ohjeota detennin.r 
nature, and unchangeable in hese, together with 

Ecliptic and its accessories being mingled indiscrimin . 
together. But as ll . :e found her way beset with 

dimV i ch could by no other mean- be surmounted 

than that the new arrangements I 1, moal have appro- 

priate language to express them ; which, not fiffatmg, she was 
ped to give new and technical significations to such words 
as most nearly gave her meaning. The first word of the 

la, however, a term composed far the occasion.* 
But be: !v in the ami 

mind were fully developed, the nascent subject shot forth 
new branches, and these still others, until the three B 
Systems, with each its accessor nd, and their 

-ections ehowi ♦•ing permanent or movable 

cording to their systems. When the fipirc representing these 
was completed, the author being asked to explain it. Mid, ' It 
is three things, instead of three hundred.' 1 ere* 

at length in * noU on p*go TIL 



8 TBEFACE, 

the learned astronomer find that he had gained an advantage, 
if, in speaking on astronomical subjects, he could use terms so 
general, and yet so clearly defined to the comprehension of the 
young, as are the Spherical Systems ? 

But in venturing so far from the beaten track, much read- 
ing and reflection were required ; lest, in forming a new and 
useful ladder on which the young might climb to high sub- 
jects, the grand edifice of Astronomy should be marred. 
The growth of the work was therefore slow and laborious. 

In the study of the Terrestrial Globe — indispensable on ac- 
count of the false impressions given by comprehensive maps, 
especially maps of the world- — the author has also devised 
some new and useful methods ; particularly, that of the sweep- 
ing measurement of all distances from the observer's position, 
by terrestrial Almacantars. 

Since no human production is perfect, notwithstanding 
care, this work will have its errors ; but the author will cor- 
rect them as soon as known, whether indicated by friend 
or foe. She regards herself as peculiarly fortunate, in 
having written at a time when Herschel's " Outlines of As- 
tronomy" had recently been revised, and Humboldt's " Cos- 
mos" just issued from the press, — the best and most unim- 
peachable of authorities. 

The opening sentence of this work is not an idle flourish ; 
but a pledge conscientiously redeemed, by so managiDg the 
subjects as to enlarge and invigorate the mind, and to estab- 
lish such mental habits and tones of thought, as shall lead the 
pupils, as they advance into life, to moral as well as intellec- 
tual greatness ; — to become the servants of God, and the 
friends of man. 



CONTENTS 



GHAPTKB T. 
Introduction. — Definition of Astronomic*] Geography. — The 

Globe. — (Jravitation. — The Nature and 

hern, n* applicable t<» Astronomical Geogra- 
phy, vr the Doctrine of the Sphere. — Definition! 15 

CHAPTER II. 

Usee end I ttial and Terrestrial Globes. — 

. — 'lli. OoDBiellatJona, — Anti- 
que M 

GHAPTKB III. 

vul.ir 
I be \i> m - li the I arth lim- 

ifx-i- 

pal Planeti and Satellites, — Comets,— 

Dees. — Sir John Hersebel'i Qlostration el the 

GHAPTKB IV. 

Distinction of Positioni u nent and Movable 41 

OHAPTKB v. 

The B 

- roth, — The Prime Vertical oof an 
East and W. -t Lino, an .'««r. — 1 >- ftnitions. . ■ 

GHAPTKB vi. 

Earth, Diun ■ 

CHAPTEB vir. 

Sign Ketroccssinn i 'ointl 

caused i anon of t] 

d of the Bon in 

Illustrated by a Father's E 
Son 



10 CONTENTS. 

CHAPTER VIII. 

Time and Space. — Periodicity. — Secondaries of the Equator. — 
Terrestrial Globe made for the London Observer. — 24 Semicir- 
cles measuring the Equator into 24 equal parts of 15° each — 
This Unit in Space equal to an hour in Time. — Terrestrial 
Longitude — How Reckoned — How Calculated. — Circumpolar 
Stars 82 

CHAPTER IX. 

Terrestrial Almacantar Circles — How Used to Divide the Earth 
into Six Belts ; being an Easy Method of obtaining a General 
Knowledge of the Distances of all Places on the Earth's Sur- 
face from our own Position 92 

CHAPTER X. 

Changes of the Seasons, and the Causes 99 

CHAPTER XL 

Permanent Positions arising from the Intersections of the Systems 
of the Earth and Heavens. — The Tropics and the Polar Cir- 
cles. — Different Planets have their Axes at Different Degrees 
of Obliquity.— The Five Zones 108 

CHAPTER XII. 

The Intersection of Spherical Systems. — That of the Earth with 
that of the Observer. — Eight Central Angles of the Intersect- 
ing Spheres. — Latitude and Longitude the Foundation of Geo- 
graphy. — Of Navigation. — Means of finding Latitude 119 

CHAPTER XIII. 

Great Circles can, by their Planes, be transferred from one Sphere 
to another. — Smaller Circles cannot. — Observer's Line and an 
Imagined Ray of Solid Light made mediums for transferring 
Circles of Latitude and of Daily Motion. — Comparative Length 
of Days and Nights. — Right Sphere. — Parallel Sphere 126 

CHAPTER XIV. 

Spheres. — A Right Sphere ; a Parallel Sphere ; an Oblique 
Sphere. — The Atmosphere — Necessary to Man's Respiration; 
that is, his Life. — Aerial Tides. — Oceanic Mountains 135 

CHAPTER XV. 
Parallax. — Refraction. — Reflection 145 

CHAPTER XVI. 

The Moon. — Its Poetic Influence. — Size. — Position. — Three Mo- 
tions. — Orbit. — Selenography. — Nodes. — Gravitation. — Tides. 
— Light of the Moon. — Eclipses 153 



11 

CHAPTER XVII. 

•h.— Tin- Oblique Sphere.— Earth'i 
rat< >n in her Orbit — Gravitation. — Centrifugal Force. 

— Bun'i Altitude, . w York. — Triangle i»t" Time.. .169 

GEHAPTBB XVIII. 

th of the Daya and Right* — 
Mia aod Appearance of the Sun.— ►The Obeerrer at N«w 
rh «.»n the 10th of Ma j. — What the Length ofbii Day, Ac, — 

at Stockholm ; at Cape Horn ; at 
1S1 

CEAPTKB XIX. 

therms.— Causes of Exception to the Law that 
.•!-• 190 

CHAPTER XX. 

inc. — The Educated live. — Much 
'203 

SB xxi. 

. 

— 'I and ()i.- 

aeo ad Day, — The Astronomic*] 

. Tune "t" the Solar and 

BM II Of the Kquinoctial 
no E<juinoxed 213 

CHAPTKB XXII. 

Irregularity in S lar Day* — The Mean Day found 

by the Clock. — Two 

Causes d the In "-Obliquity of the 

tnequaJ Motion in herOrbil performing 

equal A r — Diapoea] of the odd Bour* and 

Mi:. : the Calendar. . 

CHAPTER xxill. 

Astronomy doubly honors God, in r | < >)>- 

•~ and to Mind — l> 1 I the Tana — Nature of Mind, 

■ mceni . — 
taone who tir-t enhtrateo tin- Science. — Ohmcoe, in:.. 

I'riesU, Qreeke. — I 
Sch iea, Anaxa 

tone, Pythagoraa, Damo, Philolaua. — School <»f 

Arvfttillu*, Timocharia, Ariatarch . 
Hij.|.ardiuj. 



12 CONTENTS. 

CHAPTER XXIV. 

History of Astronomy after Christ. — Ptolemy — His System.— 
The Almagest. — Historical Great Events quicken Inventive 
Genius. — Discovery of America. — Copernicus — His System : — 
Compared with Ptolemy's. — Tycho-Brahe. — Kepler — His three 
Laws. — The Discovery of the Telescope. — Galileo — His Perse- 
cution. — Huygens and others. — Sir Isaac Newton — His Excel- 
lent Character. — Great Law of Universal Gravitation. . . . .249 

CHAPTER XXV. 

Astronomy as left by Kepler and Newton. — Mathematical As- 
tronomy. — Optical Astronomy. — Bodies added by Discovery 
to the Solar System. — Aerolites. — Tremendous Shower at 
Aigle in France. — Meteoric Shower in North America, 1833. — 
Terrible Appearance at Crema. — Franklin's Discovery.— Morse's 
Invention. — Changes in the Stars. — Appearance and Disap- 
pearance of the great Star in Cassiopeia. — The two Herschels. 
— Sir W. Herschel's great Plan and Labors in gauging the 
Heavens. — Continued by Sir J. Herschel. — The Telescope. — 
The Discovery of the Southern Heavens. — Great Discoveries 
of Stars in the Milky Way. — Sublime Hypothesis of Sir "W. 
Herschel concerning the Motion of the Sun. — The Milky "Way 
the paramount Circle of the Heavens 264 

CHAPTER XXVI. 

Atheism Unphilosophical. — God is especially Manifested in 
Adaptations. — Man is adapted to the Earth, the Air, and the 
Sun, and they to him. — Man's dignified Position — His Immor- 
tality — His high Moral and Religious Duties Illustrated by 
Gravitation 2*78 



NOTE TO TEACHERS. 



7%s authors views concerning a Method of Simultaneous Set 
and Study. 

To read with case and tl . LJ •lishment, and 

to be acquired by much practice. And whoOTOI wiO look book npon 
hia cmrly school-days, will And that nothing Ki man indelibly im- 
pressed upon his mind than tl. ttng- 
lessons. Following these ideas, the author— an experienced tear: 
has laid it down as .11. in nil 
possible oases, be taught to read what they st>< 
they read. It is a plan which makes 
important purposes, saving tl. th of the inatz 

■ 

is book is thereforo arranged forma 
two purposes; iy as 

connected with Geo,.- n it 

Jy and recitation, 1 
by tfcs t. aohsjr. 

suppose the class to begin the book with I f the 

term, and that the Globes stan d in lull view. If 

ass understand tha* mence a study, on which 

they are, e£ t ran, to be examined, it will qui 

their powers of atterr I thai 

they | read the lessons 

wsU f— distinctly, audibly, and with correct articulation, pronnnola- 
tion, and emphasis. og, should, 

if possible, be as much as tl I day. 

I the common practice with good tea- 
ing the meaning of words and 

that the pupils understand them. T asizo 

prop i 

the text will mutual: .-ach other blackboai 

Indiapsjnaabk so goo 1 feaoohing. 

Ql having read the lesson, the questions at the I 
the page, or others, can, at the option of the teacher, be ■ 

■ 
books. Thus the knowledge ibjeot will re- 

entering their n 'he same t ig the 

eorrect manner of reading aloud. 



14 NOTE TO TEACHERS. 

Towards the close of the term, we recommend that the class give 
their attention to the subject-matter y as at the first, to the manner 
of reading. 

By proposing this method, with a book designed to afford a con- 
nected view of an important subject, we do not expect, or desire 
to dispense with reading-books in schools. Those are needed for 
first lessons; and they afford rules and examples for Bhetorical 
Beading. But the teacher, whose classes read their studies in the 
method here laid down, will find his pupils prepared to learn rhe- 
torical reading, — as the writing-master, who first teaches a good 
common hand, finds his scholars prepared to learn the flourishes of 
ornamental chirography. 

In the summer of 1840 the author of this work was elected by 
the freemen of a parish in her native town, Kensington, in Connec- 
ticut, to superintend, for a season, their Common Schools. The 
classes of the five existing schools were examined together at tho 
close of the summer term by Henry Barnard, Esq., State Superin- 
tendent of Schools, — by the eminent Educator to whom this work in 
dedicated, and many others. Mr. Barnard's Report of the results, to 
the State Legislature, was extensively quoted, and referred to as 
describing an improved method in education. It was thought 
wonderful that so much was accomplished in so short a time, 
especially in the use of language, oral and written ; not only in 
reading naturally and without toning, but in spelling correctly, and 
in composing off-hand on subjects given at the time by the exam- 
iners. Our classes had studied what they read, and they had 
read what they studied. They read understandingly, and they 
became familiar with the right spelling of words, and their arrange- 
ment in sentences ; and thus time was saved for the practice of off- 
hand composition, and for other purposes. 

The Exercises between the chapters are written in a more free and 
conversational style than the chapters themselves. The author 
supposes the teacher will probably give these to the pupils to study 
between the times of reading the chapters, for the purpose of di- 
recting their observations to be made on the Starry Heavens and 
on the Globes. But every good teacher has his own methods. 



ASTRONOGRAPHY, 



OR 



ASTRONOMICAL GEOGRAPHY. 



CHATTER I. 

Iimi' -DlfUUJJ H HKUI f;FOf;r. vrnv. — TriE 

Astih ial Tbuuhtha] 

SPHERE, AS Arri.KAIU.K T<» A 1 1 ft '\< >M K \L 
OEOGRAPQT ; OR, 'I UK. — I'KHMII 

1. :' i work of elementary instruction, in 
any i oe, should perform the <luty 

ientiotu teacher, — desirom not 
npik in that one science, but t<> pro- 

iiK-nt; and most, in the beet 
thi: g 

2. which we treat tends to cult i \ 

and adoration of the (; '"1 of 

and in the habit i serving his works, 

th and in the 1 1 and, alao, to 

re strength and - ning powers, and 

ition; — kinds of improvement 

. • ion of moral sod intellectual gn 

BBS. 

describes the 



ima I. — 1. In what «pi: \v«.rk to 

teach any particular asisnoe, perfbra 

ihoold t)jp taachtr seek 

most I — 'J. In what 

rmphy or Astmno^raphy at .• youth f 

at arc these two kinds of imj.: 



16 man's home, the earth. 

Earth ; and to us, whose home is in this planet, no 
knowledge can be more interesting. But the condition 
of the Earth, signally depends upon the Sun, is much in- 
fluenced by the Moon, and in a lesser degree affected by 
the other heavenly bodies. So that the very foundation 
of Geography is laid in Astronomy.* This science treats 
of the heavenly bodies, and of the Earth, as composing 
one of their number; so that there is one portion of 
Geography which is Astronomy, and one portion of 
Astronomy which is also Geography :\ and these parts of 
the two sciences, together compose Astronomical Geog- 
kaphy ; or, in one word, Astronography. 

4. The Artificial Terrestrial Globe represents the great 
globe, or Earth, which man inhabits. To the centre of 
the Earth all things upon its surface tend, being drawn 
towards that point by a force, called the Attraction of 
Gravitation. An Artificial Globe cannot, in this respect, 
be made to resemble that on which we live ; but it must 
itself, with whatever is upon it, be attracted to the Earth. 
With regard to every individual of the human race, down, 
signifies directly towards the centre of the JUarth ; and 
up, directly away from that centre ; and this is the case 
on whatever part of its surface any one may live ; whereas, 
on this Artificial Globe, there is but one position, which 
we term the Upper Vertex, where a little figure, repre- 
senting a man, could be made to stand. His feet would, 
in that place alone, point towards the centre of the arti- 
ficial globe, and, as ours do, towards the centre of the 

* Astronomy, from two Greek words, asrep, a Star, and vo^ 
a law. 

f Geography, from ys, the Earth, and ypa<pe, description. 

3. Define Geography : On what does the Earth's condition de- 
pend ? Define Astronomy : What, in view of these definitions, 
is Astronomical Geography ? — 1 What is represented by the Ar- 
tificial Terrestrial Globe ? What force is here spoken of ? What 
effect, with respect to the Earth, is produced by the Attraction 
of Gravitation ? In what respect is it impossible that an Artifi- 
cial Globe should truly represent the Earth ? With regard to 
mankind, what direction is down ? What direction is up ? What 
difference is there between the Earth and the Artificial Globe, in 
regard to a position on which to stand ? 



m i>r.su;\ IK. 17 

arranged, bo thai we on 

make the Upper Vertd the plaos of the ftnai 

Observer. 

5. r is an imaginary personage, to 

d on the Earth many of the definitions of 

For the place of this 

ire ftnall continue to dm the term Upper 

ir first lessons in this science, should 

r kept in their new, with his place of 

: it is intelligent mind beholding things 

rtain place on the Earth's 

•'.•:;. After* 

may slone be used, ss circum- 

stances dictate : u nr u the Meridian of Lou- 

don.'" lias of the Observer at London; u the 

Zenith of the ( observer at 
Boston. 

6. 
mous; but in th lifier- 

ence. The n £ used in IfathemaJ 

and the port f die 

properties of t he & 1 Spht r 

• swe hare the phrase "the Doctrine of the Bph< 
Without som< I doctrine, 11 no 

can be made in A graphy. A Globe or 

Sphere is a solid b<>< wk iek il 

• i this, thai 

\\U" i> a / f 11" Spl 

7. ps as to be in 

• line, coi 

the Sphere. 

5. What is ■ -»'. What <lif- 

fercooe w * be terms 

br Spheric* f What can you ■ f thi BoIm 

this « 1* - ti f i : 
What is a Radius < : v may we sup 

pose the Diameter of a Sphere to be constituted I 

'J* 



18 DOCTRINE OF THE SPHERE. 

to two of its radii. Any straight line passing through 
the centre of a Sphere, and cutting the surface in opposite 
points, is a diameter. The diameter is the longest straight 
line which can be included in a Sphere, All the diameters 
of a perfect Sphere are equal. 

8. The Earth is not a perfect Sphere. Its diameter at 
the Equator is longer by 26 miles than that from north 
to south, which is identical with the Earth's axis. By 
being thus a little flattened at the poles, the Earth ap- 
proaches in form to an oblate spheroid. Yet its variation 
from a perfect sphere is so little, that for any purpose, 
appertaining to our present study, it is not necessary to 
notice the difference ; but we are to study the Globe as if 
the Earth, which it represents, were a perfect sphere. 

9. We find drawn around artificial globes many circles, 
some of which are great circles, and some small or lesser 
circles. A Great Circle is one whose plane divides the 
Sphere into two equal parts, or Hemispheres. A Lesser 
Circle is that whose plane divides the sphere into two 
unequal parts. To understand this, we must consider 
that to every circle belongs a plane, as well as a circumfer- 
ence and a centre. 

10. For illustration, suppose I take this round apple to 
represent a Sphere. Any Sphere, cut by a plane which 
passes through its centre, will be divided into two equal 
half-spheres, or Hemispheres ; and the meeting of the 
plane with the surface of the Sphere will be a great circle 
of that Sphere. I hold my knife level, and cut the apple 
through the centre. The line of the divided skin repre- 
sents the circumference of a great circle of the little Sphere, 
and the plane within, is the plane of that circle; the 
middle point being the centre. Suppose the halves of the 



T. What further may be said of the Diameter of a Sphere ? — 
8. What is said on the que stion whether or not the Earth is a 
perfect Sphere ? What kind of Sphere is it ? — 9. What are the 
two equal parts or halves of Spheres called ? What are Great 
Circles of Spheres? What are Lesser Circles? What three 
things belong to every circle ? — 10. How may the circumference, 
plane, and centre of a circle be illustrated ? 



DEFICIT! 



19 



appl< ^ether, so that no plane can be soon, 

the plane to be attended out to any 
listanoe from the apple; like this paper circle 
which i> inserted between its two halves. 

1.4 




11. Tl 'V an<l DiomtUr of any Great 

and diameter of 
that 5 uneter may be termed an 

ra; farif about which it might revolfo, 

if there ' i m| it in motion. Any axis of a 

• ■ and Polei eonn< 
with that axis may be (bond. For the meeting of the 
axis with I two opposite points of the Sphere 

68 of that axis. And / 

tki (iris inn fs ,tf 

A line it at right 
angles, oi Licnlai to a plane, when it does not in- 

cline to either 

T€ y are those 
which the axis cuts v .-S between the Gh 



10. How can yon f«»rm an Kdeaof tl. lacing 

led \ — 11. W I any 

Sphere equal to I sphere be \ 

f.-r it- fi\i- f BuppoM an axis of a Sphen to bi L-iv.ii.uh.it may 
be known f I beloogiqg to any 

It. Define the Leuer oxia. 



20 



OIECLES THEIR MEASURE. 




Circle and the Poles. Of the axis of the Earth, the 
Equator is the Great Circle; the two Tropics and the 
two Polar Circles, and all 
circles of latitude are Less- 
er Circles; and its poles 
are the Poles of the 
Earth. 

13. Angles are mea- 
sured by arcs of circles. 
An arc is any part of a 
circle less than the whole, 
and is said to be an arc 
of a certain number of 
degrees. To find the mea- 
sure of arcs and angles it 
becomes necessary to di- 
vide the circle (that is, any or all circles) into a certain 
number of equal parts. By common consent every circle, 
whether great or small, is divided into 360 equal parts, 
called degrees. For the purpose of exact measurement, 
degrees are divided into minutes and seconds. A minute 
is the 60th part of a degree, and a second, a 60th part 
of a minute. A degree of a Great Circle of the Earth is 
60 geographical miles, or 69* English miles. Hence a 
minute and a geographical mile are the same measure, 
but both exceed the English mile. 

* When the circumference of the Earth was estimated at 
25,000 miles, it was usual to state the number of statute miles 
of a degree 69-J-, which number was, even at that calculation, a 
little too large ; since 360° X 69i=25,020. But taking the number 
now more generally adopted from Sir John Herschel, 24,856, the 
nearest approach to correctness, without running into inconve- 
nient fractions, is 69 statute miles to a degree; since 360° X 69 
=24,840, which approaches within 16 miles of the present calcu- 
lations of the Earth's mean circumference. 

12. What is the Great Circle belonging to the Earth's axis? 
"What the Lesser Circles? — 13. How are angles measured? What 
is an arc of a circle ? What must be done in order to obtain a 
method by which the measure of arcs can be determined ? How 
are circles divided ? What more minute divisions are used ? If 
we take a Great Circle of the Earth (which is the measure of the 
Earth's circumference), to what is each degree, or 360th part, 
equal ? How is this reckoned ? (See Note.) 



MUTUALITY OF ANGLES A5P ARCS. 



21 



14. We insert a diagram to illustrate the division of 
I the measures of iDgl68. The circle A.BCD 

is divided by two diarn* ft r.s A and B D, so crossing each 




xio- 



other at : I >UT equal 

- at th»- et-ntre are equal, and Uiey 
are all r Sii •• the measure of the circle is 

860 degrees, that of a quarter of a aide b ^ (| 
An i subtends half a right angle, and an an of 

■ 

ally, all angles are mscwtred ty tts ares 

and it makes no difference whetb r 

• nee of the circle, whose fcrc measures the 

an^le, be great or small. The two circles of the diagram 

ag a common centre, are ( tf 

I* ),l>irt,l at tf ■ 

oriiono0jf« It' 



1 t If n dnle i- dividbd by two diameter**, 
centre, making equal angles, what are those angles f 

! i th«- circlr witi- dn 
• qual angle a, \ 1 these angles be »iil»t»n I. -1 } 

t bese angles f — I onfoana] principle 

angle be placed at a common las I 



22 A SPHERICAL SYSTEM. 

its sides include 90 degrees in the smaller, they will in- 
clude 90° in the larger circles, and so of any number of 
circles and any number of degrees. 

16. When a Convex Sphere is so inclosed by a Concave 
Sphere or hollow Globe, that the centre of the Convex is 
also the centre of the Concave Sphere, then these two 
Spheres are Concentric ; and the axis of the Convex and 
the plane of its Great Circle may be produced to the Con- 
cave Sphere, becoming its axis and Great Circle, — the Poles 
in each being, by definition, the extremities of the axes. 
This is the case with the Convex Terrestrial and the Con- 
cave Celestial Sphere by which it is surrounded. 

17. A Spherical System, as we shall use the term, is 
composed of the Axis, Poles, and Great Circle of a Sphere ;* 
and may be accompanied with certain adjuncts ; as the 
'parallels of the Great Circle, which are small circles, 
lessening towards, and finally vanishing in the Poles ; and 
the secondaries of the Great Circle, which are great circles 
cutting it at right angles, and crossing each other at the 
Poles. Thus the Axis, Poles, and the Equator of the 
Earth, are a Spherical System, which may be considered 
with or without the adjuncts or accessories, which are 
parallels of latitude and circles of longitude, or hour 
circles. . . . When any body is in circular motion around a 
central point, that motion is reckoned according to the 
degrees of the circle passed over, and is called angular 
motion. The distance between any two bodies, or between 
any two points situated on the same circle, is the number 
of degrees of the part of the circle intercepted between 
them. This is called angular distance. 

* See Fig. 1. 

16. What are Concentric Spheres? — 17. What is here called s 
Spherical System ? What is angular motion ? What is angular 
distance ? 



ITIE FIRST PROBLEM. 






l — W« reeoanMod that Ihese 

. 

and tin* 
i 

Igfjd if in In- tir.-t §j 

wrong line often shows whefj 

It is 
* an auth. I 

that :i b.*.k should b»* bled with be-lit1 

r<.->cntat; 

e Nn.k on i 
cramped . 

an;." ii so fundamental, ti. at w» recommend that questions on 
t}>> Hibjed be frequ< ntly given to the class. 

• 

i »xpe< t tl - rson will 

i map 

the brazen mer will find, direct!-. 

Philadelphia M from tin 
I 
place sought is in north latitude) as i 

will than be m | .ally 

how many 
will be as circle be to IS equal parts, of 

how many degrees will be each part ? If into 24 equal pal 
how many degrees will be ea< - .t a part I 

of a circle is 4 degrees! How greai a p 
S0° f How great a part is 15° t How great a par 
I 90° f ; 

be, define the position of tho 
Earth- Equator, as to the oceans, seas, continents, countries, and 
islands through which it i 



CHAPTER II. 

Uses and Differences of the Celestial and Terrestrial Globes. 
— The Fixed Stars. — Their Distances. — The Constellations. 
—-Antiquity of Astronomy. 

1. While the two Globes, the Celestial and Terrestrial, 
are placed together before a class, who are more or less 
acquainted with geography, the pupils are easily made to 
conceive, that the Terrestrial Globe, covered as it is by a 
continuous map, represents the Earth ; and thus they 
readily understand its use. But they find difficulties in 
the study of the Celestial Globe, which partly arise in 
consequence of its differences from the Terrestrial. 

2. The Celestial Globe is made of the same size as its 
mate, the Terrestrial ; whereas, the Sphere which it rep- 
resents is immeasurably larger than the Earth. The 
Terrestrial Globe is convex, as is the Earth which it repre- 
sents. But the Celestial Globe, while it is convex, repre- 
resents the vast concave of the Starry Heavens, which 
concentrically surrounds the Earth. 

3. While the Terrestrial Globe presents a familiar map, 
dividing its surface into oceans, seas, islands, and conti- 
nents, the Celestial Globe is covered with uncouth figures 
of all monstrous things — strange men and women, 
mingled with beasts, birds, fishes, and serpents. These 
grotesque figures represent the Constellations, into 
which the surface of the concave Heavens is divided, — as 
is the convex surface of the Earth into seas and countries ; 
and as the Geographer learns them, and the cities which 
they contain, from the Terrestrial Globe, so does the 
Astronomer learn the names and places of the Constella- 

Chapter II. — 1. Which of the two globes is most easily under- 
stood, and why ? — 2. In what respects are the two globes different ? 
What is here said of the concave of the Heavens ? — 3. What do 
the uncouth figures on the Celestial Globe represent ? What are 
Constellations ? 



thi: ICRB0FQLIXAH COM S6 

tions, and the principal stars which they include, from the 

4. Of the E o first division is into fixed and 
wane' >\ of which our Sun is regarded 
as one, ;. which do DOJ tiMy change their 

with regard to each other. The wandering 
la, are Plan eU and OomeU* The Earth ie a 
planet The wandering Btan have do place giren them 
on a Map: the Constellation* which till it, being 

who] I etare. But as the 

journey of a traveller can be made known to ■ reader who 

tphical map of the fixed p] 
through which h an the course of a wander- 

tly intelligible to the person who 

deal map, with which the Ce- 
ntered. 

5. The Sun ap pear * to ohang rition in regard to 
the fixed stars, but does nd in n-ality. I lis appa 

in thai 

oa the King . hii 

app.-*. . the 11' properly made 

:.y. I In 

nomical latitude ned from the Ecliptic, 

graphical is from the Equator. A belt in the See 

• the Ecliptic, and 

com; bite of all the p <>ids, 

is c:i Zodiac. The twelve ConeteDationfl of the 

tcshouldbel' ; al Globe, in their 

prop- :•• familial 

6. nnonnd the Earth on le ; 

they are concealed by the 
dastingraya f the Sun, 

swed through lai 
scopes. It has bft I that the 

4. What U said < 4 nrsf Of wandering stars? Bi 

-e be 
I 
What here 

.rard to the Earth, ars 



26 

also seen by day from the bottoms of deep wells; but 
this is doubted by the great traveler and philosopher, 
Humboldt, who has never found a well or mine, from 
whose depth, gaze as he might, he has been able to dis- 
tinguish stars above. The fixed stars are luminous ; that 
is, they shine by their own light ; the planets are opake, 
having no light of their own, but shining by the reflection 
of the light of the Sun. All the planets known to us are, 
like the Earth, secondaries to the Sun. If the fixed stars, 
as is believed, have, in the same manner as the Sun, 
opake secondaries revolving around them, this could not 
be known to us, on account of their immense distance. 

l J. Though the intellect of man has achieved wonders in 
measuring the diameters and distances of the heavenly 
bodies, yet it is not until recently that an approach has been 
made towards any positive knowledge of the distances of 
the fixed stars from the Earth, — other than this, that it is 
vast, beyond the human powers of calculation, or even of 
thought. But an astronomer of Prussia, Professor Bessel, 
has now determined, with a show of accuracy, the distance 
of a fixed star. It is a binary, or double star, in the Constel- 
lation Cygnus, the Swan, which, according to his calcula- 
tion, is more than half a million of times further from the 
Earth, than that it is from the Sun. Such is its distance 
that light, which moves at the rate of 192,000 miles in a 
second, would be 9J years in coming from that star to us. 
There are reasons for believing that this star is nearer to 
the Earth than other fixed stars, which are much more 
brilliant; and the fact is thus established that the fixed 
stars are of very unequal sizes. Some are supposed to be 
much larger than our Sun. Sirius (the Dog Star) in the 
Constellation Canis Major (the Great Dog) is regarded as 
the most brilliant of the fixed stars. It is calculated that 
its light and heat are 34 times greater than the Sun's; 

6. How do the fixed stars differ from the Planets in regard to 
tkeir light ? What is said of the fixed stars having, like our Sun, 
opake Planets revolving around them ? — 1. What is said of the 
distances of the fixed stars ? What is said concerning a binary 
star in the Swan ? What fact is established ? What is said of 
Sirius? 



WTBOtM anp ixvisir.i.r. 27 

but astronomers have thus far boon baffled id all attempt! 

8. . divided into riribU and ft '■ 

an 1 U\l, the Jnbuloui, Th< 

by the naked aye, are divided, ac- 

the different characters used, by 
h may be known, He largest stai qu- 

nly 18 I tided as of the first magnitude. 

isily learned 6om the 

may be known when seen in the Heavens. They 

r name, and are to the map of the Heai - 

that <>f the Earth. The Astron- 

tn, in the ( constellation 

• :• Lb London,in Great Britain. 

9. Of the i there have been counted 
about 4,000. mall compared with the tefo- 

xopic stars, or those wh to view by n 

d counted 
a small i md if n erful 

instruments l mid doll 

• sumed to exist are n< bular, 

in the Heavens, like small luminous do 

hulct, long excited the curiosity of Astronomers. 

r the magnifying power of the 

great telescope of Sir William Eferschel, round to be 

ni of the broad luminous tract 
thus re- 
solve ronomers 
believe that telescopes will yet be made, with a magnify ing 

power SUl W, that tin- wlmlr of this 

imm-'nv composed of myi itant 

Idest imagination 
to c lias the 

■ 

ongn. I >f the v! 

how many harp beei 
■ 
found to be, and bj whom f What U said < : sy f 



28 THE POINTERS AND POLAR STAR. 

general form of a great circle, which crosses the Equinoc- 
tial at an angle of about 60°. 

11. Celestial Globes have sometimes been made so 
large that the student could go within, and see from the 
centre the Constellations ; which, in this case, were painted 
on the inner or concave surface. This would give him a 
correct idea of their positions. If we suppose that such a 
large globe stood under the open sky, that the painting 
was transparent, and the globe rectified for the place and 
the hour, then the Observer at the centre might look 
through the painted Constellations of his transparent 
globe directly to the corresponding real Constellations in 
the Heavens. If, for example, he looked towards the 
north, and through the Great Bear drawn on his globe, he 
would see in the Heavens — not the figure of a bear, it is 
true, but the six beautiful stars, which, both on the globe 
and in the Heavens, form the well-known Dipper ; and he 
would see the two stars in the front, called on the globe 
Merac and Dubhe, pointing to a smaller star called Cy no- 
sura in the Little Bear ; around which, if his great con- 
cave globe were slowly turned from east to west, to imi- 
tate apparent diurnal motion, he would see the Dipper 
and the other stars revolve ; and this is the Polar- Star. 

12. The cultivation of Astronomy goes back to the 
earliest dawn of history. When Alexander the Great 
took Babylon, B.C. 331, he found reason to believe that 
this first of human sciences had begun in Chaldea, ante- 
cedent to the founding of the Hebrew nation by Abra- 
ham. In the Book of Job, one of the very earliest writings 
of antiquity, the most beautiful Constellation of the 
Heavens, Orion, is called by its present name, — as is also, 
Arcturus, a star of the first magnitude, now ranged in the 
Constellation Bootes, and the most interesting group of 
the Celestial Sphere, " the Pleiades" in Taurus. 

11. What if a transparent Celestial Globe were made so large, 
that an Observer could go into the Earth's place at the centre ? 
What would such an Observer see at the north? — 12. What is 
said of the date of the science of Astronomy ? What evidence 
have we that it had begun as early as the date of the Book of Job ? 
— 1 3. What is said of the origin of the Constellations \ Of their use ? 



) MS :v. 

. Why tl 

lestia] < Hobe, 

ot in all cases Butther gnificancy 

in n i and figures; and others oommemo- 

uniliar to anci< nt story. Neither 

countries always 1"' tract d, 

• iph< r :»\ ails himself <-t' them ;*- tl" j • 

oomer in regard t<> the ConBtella- 
:.«! strange shapes maj k n 

fix them in 1 : v. 



BX1 

Observe on : r they nro designed t<» ropro- 

I with the present 1<-— on. 
Sets] (t1«.i me- 

r fij I t.» tli.> North | 

• the 2 i boon of t 1 * * » 
day. til of the 

part 

and has mark* tains 

which the Sun :t|»i 

b t<> wlnrli 
corre-i 

A Quadrnnl 

and may !*• «•< t It 

rth. 

ill th< ii be in tl 
in w\ 

lest night; an-'. obe will hayi the 

•lope appears. '1 h- i 

atar* 

/on an ang 

• 
learning aa faat as pees it 
actual Hr.iv. n.-. the Constellation* thro 

th«- nosle hr;_'ht -tar*. Off the gTOUJ - "f ^tar.H mi or n«-ar it. < 'h 

MrretL 3oj - eonrae on the 20th of March and September,- ■< 

the time ;inoxea The line he then describee is the 

Equinoctial. 



30 THE EVENING SKIES. 

Find on the Celestial Globe the following Constellations named 
in the preceding chapter : Ursa Major, the Great Bear ; Ursa Minor, 
the Little Bear; Cygnus, the Swan; Taurus, the Bull; Cams 
Major, the Great Dog ; Orion ; and Bootes, the Herdsman, with his 
Dogs. Which of them does the Equator pass through, and which 
the Ecliptic ? What stars of the first magnitude do you find on 
or near the Equator? What on or near the Ecliptic? Name 
and describe them. 

Where is Cynosura ? Where is Sirius ? and how many degrees^ 
is it from the Equator ? {Measure by passing it under the brazen r 
Meridian.) 

Learn from the Terrestrial Globe the position of the Tropic of 
Cancer. Through what seas and countries of America does it 
pass ? Through what of Africa ? Of Asia ? How are Canton 
and Calcutta situated with respect to the Tropic of Cancer? 
How is Havana situated with respect to the Tropic of Cancer ? 



CHAPTER III. 

The Studies of the Celestial Globe may be pursued by Ocular 
Examination of the Heavens. — The View on the Earth lim- 
ited. — The Sensible Horizon. — The Solar System. — The 
Principal Planets and Asteroids. — The Satellites. — Comets. 
— The Sun and its Influences. — Sir John Herschel's Illus- 
tration of the Comparative Sizes of the Bodies of the Solar 
System. 

1. In the studies of the Earth and Heavens, by means 
of the Terrestrial and Celestial Globes, there is this further 
difference. The student having by the aid of his Celestial 
Globe, with such assistance from the living teacher as he 
may be able to obtain, learned to know the principal 
Constellations, with their most remarkable stars, can then 
go forth at evening and pursue his studies, by tracing out 
his subjects upon the starry concave of the blue vault above. 
There, by the remarkable stars through which they pass, he 
can locate the circles of the Ecliptic, the Equinoctial or 
Equator of the Heavens, the two Colures, and the other re- 

Chapter III. — 1. What further differences are here noticed 
between the studies of the Earth and Heavens by means of the 
two Globes ? 



CU tarth's cvxvfxttt. SI 

markable positions o( v. But we cannot, in the 

same manner, trace out upon the Earth's real surface the 

. the Tropics, < i r any of the 

. which belong to Geography, 

Homos, wkicA U the boundary 

: e actual • or water, which the 

huir. mely limited. In 

1 plain, it extends only three miles each 

way from tie is raised ;> feel from 

fa extent incre ase s in proportion to the ( >!>- 

•i.-n. Lei him 1"" raised 100 feel el 

ad 10 milrs in every 

From Dwalghiri, the highest peak of the 

Himalaya mountains, 28,000 feel high, if the view were 

6 might faintly see at the 
fer from the fed that 

from th< 

rity of the Earth, 
sea or on la unobetni 

ry particle of solid matter and everv drop 
alike gravitate V> ! rth ; thus forming 

around it a Globe. The particles of water moving among 

1, and the unruffl I 

i mirr.»r. An Observer's eye being 

Kloee to ita 'hat <>f a rail level on 

md. ad in a planet tangent t«> (or 

tour 

I ! . .'md is always meani 

on \< mentioned. 

ted, and the line of his 

'i will no longer M in t! \\ plane; hut hi- 

c. Whal ; s Ihs B 
natural h> 
it incrfa- 
What ii Mud in this cr-r intlfal SUmmil Dwal- 

fron these premi-'- ' ^ 
of the unruffled ocean f 

a plane tang* I tfc*l surface f What it thin plana 

parallel to, and what U it called V 



82 THE SENSIBLE HORIZON. 

Sensible Horizon will droop or dip. Imagine a line drawn 
from the elevated eye to the convex surface of the Earth, 
and passing onwards to the concave Heavens, and then this 
line revolved, — w r here it touched the Earth, it would describe 
the extreme circle of the Observer's Terrestrial view, and 
where it met the Heavens describe the extreme circle of the 
Observer's Celestial view ; and both these circles will be 
enlarged in proportion to the Observer's elevation, and the 
consequent increased Dip of the Horizon. The line re- 
volved, produces an imaginary cone. 

4. The Earth, by its convexity, gradually recedes beyond 
the circle of terrestrial vision. We will suppose a ship at 
sea, yet below the circle, but approaching the Observer, — 
the top of the mast will first rise above his dipping Horizon, 
and be seen, — then the lower parts of the masts ; and last 
of all, there heaves in sight the hull, or body of the ship, 
which is its largest part. Since these phenomena occur 
in every part of the world, and since nothing but a convex 
figure could produce them, the Earth must therefore be 
everywhere convex ; that is, it must be a globe. To such 
certainty and practical exactness are these principles re- 
duced, that the height of an object is calculated from its 
distance, or its distance from its height. 

5. It is evident that heavenly bodies will appear in dif- 
ferent positions, viewed by Observers on different parts of 
the Earth's surface ; and hence that observations made at 
any one place on the surface will not be of general use. 
Astronomers, to rectify this inconvenience, have adopted 
the method of making all calculations upon heavenly 

3. In what case will the Sensible Horizon droop or dip ? What 
line are we to imagine ? If we suppose this line revolved, what 
imaginary figure will be produced ? And what circle on the 
Earth will be produced by the revolution of the touching point ? 
If the supposed line meet the Heavens, what circle will it there 
produce ? (All these lines and circles the pupils may be taught 
to illustrate by drawing them on a blackboard) — 4. Illustrate by 
the appearance of an approaching ship. State the argument by 
which such phenomena prove the convexity of the Earth. Have 
these principles certainty and utility ? — 5. On what point have all 
Astronomers agreed as the place of Astronomical observations ? 
Why was it found necessary to come to such an agreement ? 



THE SOLAR SYSTEM. 33 

bodies, as if all ni them from the same ipoi ; and this 
binary point of Astronomical view, is to osufr 

the Earth, 4« toe. 

IB . ; It is floating in spaep; 

but : •' in the wind Foi not more has the 

railroad an a] I track, than lias the Earth it- path 

in spao.\ To other worlda — and raefa we deem die stars 
to be — the Earth a] (tar. It belong ronp 

of O which tli- SUN (or £0/, as called 

oentral louroe of light, of heal 

:. did which belong to ihe Solar System, 

in the first place, th< 'f, whose 

-87,000 miles. In the second place, there 
are tl b, of which sight are principa] 

i, in the order of their dial 
- ■.. are as follows: Mercu r y y V Tth, 

Mart, Jupiter \ Satun \ or Il< r 

Lertr 

8. Besides I 
several small. Planets, 

ry 1 ' .- ta, as the] 
aboot the Sun, and ire thus distinguished 
iss of bodies belonging to the 
termed Sboovdari V\ \ v 
moonSy or sat* These rerolve around certain of 

time carried with 
1 '• * • Secondary Plan* 
are /-one. Of these 

1 has .... 1 (Jranne or EEenebel . . 

1 N-]»tune or Lev. rri.r . . 2 

6. Whcr- 

What n th» fl 
the Sun ? 

• — s . What nd wlisre n r < 

iry Planet*'? What in pa -comlary Planet* t \\<>w 

many arc there known to be in the Eh B, and to what 

FlaotU do they belong t 



34 THE COMETS THE EARTH. 

9. The Comets are the fourth class of bodies belonging 
to the Solar System. They revolve about the Sun in 
orbits very elliptical. They are divided into Interior and 
Exterior. The interior Comets are those whose orbits are 
at their aphelion, or greatest distance, from the Sun, 
wholly within the range of that of Neptune, the outermost 
of the known Planets. Of these there are six, whose orbits 
and periodic times have been calculated ; and which re- 
turn in periods of from three to seven years. Of the ex- 
terior Comets, the number is unknown, but it is supposed 
to comprise at least 500. In 1847 the catalogue of those 
observed amounted to 178. 

10. "Comets," says the Baron Humboldt, "possess the 
smallest mass, and occupy the largest space, of any bodies 
in the Solar regions." It is only the large Comets, or 
those which come very near to the Earth, which are visi- 
ble to the naked eye. They appear unfrequently, and at 
such irregular times, that the ancients supposed them to 
portend great and disastrous events — such as war and 
pestilence. 

11. The Earth is nearly 8000 miles in diameter. It is 
larger than the two Planets, Mercuiy and Venus, — which are 
called Inferior because their orbits are within that of the 
Earth ; but our Planet is very much smaller than the great 
bodies Jupiter, Saturn, Uranus, and Leverrier. These four 
Planets, together with Mars and the Asteroids, are called 
Superior Planets, because their orbits are without that of 
the Earth. 

12. The Earth's distance from the Sun is 94 millions 

9. "What is the fourth class of bodies belonging to the Solar 
System, and into what are they divided ? What is aphelion? 
What are interior Comets ? What exterior ? What is said of 
the numbers of the Comets whose times have been ascertained ? 
Of the conjectural number of the Comets belonging to the Solar 
System? — 10. What is said of Comets by a celebrated writer ? 
What is further said of Comets? — 11. What is the ordinary esti- 
mate of the Earth's diameter ? When are Planets said to be in- 
ferior? When superior? What Planets are in each of these 
classes ? What comparison of the Earth's size to that of the 
other Planets is here made? — 12. What is the Earth's distance 
from the Sun ? 



* TEAK, MONIH, AND PAT. 35 

of miKs. One million of inilrs is move than forty i • 

urth, and our distance from 
Mercury's distance is i little more than 
a thi , and Venus a tittle more than two- 

thirds. Mar* md a half the Earth's 

able; Jupiter, the largest of all the 
- the Earth's distance from 
B urn. with 

Bus 19 — and Lever 
• t light and heat as our- 

13. id times as well 

set ] time which the Earth takes in moving 

S • died, in our lang fear. It 

The time of the 
9 is called b day y and is 
me of tb 
is si. baa our own, 

M i* also their day. Tl !•->♦■• sul»j»vts ar^ fully tn-ated in 
the ta 
It 

■ 1 1 1 J LT Hi! • 

moonth* . in order to ah id< 

year 

alwn >f a month, the yearly 

moi. i !)•• to thl • r than the L 

moftt . /. Latin word I <. the Moon. 

A /. time i i n the chai 

of the Moon, M !i again, 

15. To rei which belong to the 

bich 

and k ta. Of all these bo<: 

shines 1 or i> luminous The others all 

tli.-r j r i r 

I'lniiH*. compared with that ot the Earth! Bj what m Saturn 

of t: 

ftg Mooo'i revolution iroond Um Earth I— 16. RocapttulaU ti^j 

bodjci which belong to the Solar System. 



86 "the great sun himself.* # 

borrow their light from him, and are thus known to be 
opake. The bodies belonging to the Solar System are 
of different densities. Jupiter is less dense than the 
Earth. A portion of that Planet, equal in bulk to the 
Earth, would weigh only a quarter as much. The same 
portion of the Sun would weigh still less ; its density being 
to that of the Earth as 1 to 4J. The Sun's density is 
about equal to that of water. 

16. The Sun revolves about its own axis once in 
25 days ; as is known by the movement of certain dark 
spots upon its disk. Astronomers believe these spots to 
be openings in that wonderful investment of fiery light 
and radiant heat, with which the Sun is surrounded. It 
is supposed that within this, as these dark openings indi- 
cate, may be an atmosphere of clouds, genial to life ; and 
that beings of a high order may have the Sun as their 
magnificent abode. His surface is 1,400,000 times 
greater than that of the Earth, and 500 times greater 
than all other bodies in the Solar System combined. 
That the Planets are inhabited, there are so many reasons 
to believe, that no rational mind can entertain a doubt. 
God made them, and he does nothing in vain. 

17. For aught we know, the Sun may be the blessed 
abode of glorified spirits, who have passed through a puri- 
fying process in other regions. That, however, is mere con- 
jecture. What we know is, that of all material objects, 
the Sun is the most glorious image of his Maker. By his 
attraction the Solar System is kept in place and in order. 
By means of his genial warmth the air is attempered for 
respiration, without which there is no animal life. The heat 
of the Sun keeps the waters in a fluid state, thus giving a 

15. What shows the Sun's superiority to all the other bodies 
of the Solar System ? How do the bodies of the Solar System 
compare with each other in regard to density ? — 16. What revo- 
lution has the Sun ? What is said of the spots in the Sun ? and 
what do some suppose concerning the interior surface ? How 
much is the Sun's surface greater than that of the Earth ? Than 
that of the other bodies of the Solar System combined ? Does your 
author believe that the Planets are inhabited? — 17. What con- 
jecture has been made concerning the Sun as a place of habita- 
tion ? What do we know of the Sun ? 



Oil OXUSTRATl ;? 

e to myri e same heal produoei erap- 

trhich clouds are formed, and dews and rains 
at of tin 1 Sun thus nourishes all v. 

r On animal creation. 

intain of light, which, falling on the 

t tin 1 DniTene 91 is lifted, and man becomes 

of the beauties of external nature. Utility, a- well 

as beauty — improvement) as well as pleasure, i> conferred 

upon man by th- .;, which wo OOUld not 

■ the light of the Si n. 
l^. We hare not famished an engraving of the Solar 
that Buch often hinder tin* sub- 
impressions which descriptions might otherwise gi?e^ 
and so I m] i t .• Astronomer, 

ontempt, in the following 
, paper diagrams, m eonreying no 

e illustra- 
isary. We should i try them so as not 

vt.* 

19. " V. 

, u with j to 

d of the i 
:' our lyal 
Choose any well- field or bowl ( m it 

place a l feet in diameter ; this will represent the 

re pre s en t e d by s grain «'t' mustard- 
seed, on • • in diameter 
I>ea, on a «ir t in diame- 
b also a pea, on a circle of 

# 1 male Seminar. 

agO fUT&TiJ 

tanurn. k> that in a large room t) 

/. with i] well re| 

..• actual 

min<)«, sad snisli oar sonss p t i ons 

■ has do engraving of the Solar 
for thin work ? — 19. What nay 
and orrerica ? (tire Home acc> 

System, aa to the different aizet of the several bodies, axiJ 
comparative diataocea from the central body. 

4 



38 



OF THE SOLAR SYSTEM* 



rather large pin's head, on a circle of 654 feet; Juno, 
Ceres, Vesta, and Pallas, grains of sand, in orbits of from 
1000 to 1200 feet; Jupiter a moderate-sized orange, in 
a circle nearly half a mile across ; Saturn a small orange, 
on a circle of four-fifths of a mile; Uranus a full-sized 
cherry, or a small plum, upon the circumference of a circle 
more than a mile and a half; and Neptune a good-sized 
plum on a circle about two miles and a half in diameter. 
As to getting correct notions on this subject by drawing 
circles on paper, or, still worse, from those very childish 
toys called orreries, it is out of the question." 

Table of the Magnitudes, Distances, and Revolutions of the 
Principal Primary Planets.* 



NAME. 


Diameter. 


Distance from 
the Sun. 


Annual 
revolution. 


Diurnal 
rotation. 




miles. 


miles. 


years, days. 


hours. 


Inferior j Mercury . 
Planets, j Venus. . . 


3,200 


37,000,000 


88 


24 


7,700 


68,000,000 


224 


23J 


Earth . . . 


8,000 


95,000,000 


365£ 


24 




r Mars .... 


4,200 


142,000,000 


1 321 


24J 




Asteroids. 


.... 


.... 


.... 




Superior 


Jupiter . . 


89,000 


485,000,000 


11 314 


10 


Planets. 


Saturn . . 


79,000 


890,000,000 


29 170 


10* 




Uranus . . 


35,000 


1,800,000,000 


84 5 


94 




Neptune. 


37,000 


2,850,000,000 


164 225 












Table of -' ifl situated between the i Mmft and 

Jupii-r. It will be tee n tin! the four principal ;uv Vesta. Juno, 
oa, and Pallas. The finfl dlBOOTere 1 WM I 

•\w Beoood was I'alla.*, by M. Olbers, OJ 
Brcmcu, in IS"-. Mr. Hind, of England, baa discov< 
era!.* 



N\ Mr- 



Flora 

Meti* 

A*trea 



fhm 

P*U<U 

Eyerie 



Diameter. 




Annual 
.ti-.n. 


■fln 








.... 


810, 




98 




- 


3 




.... 


. 


1 




.... 




1 


261 


.... 


i 


3 


285 







4 


61 


1,400 




4 


114 




. 


4 




too 


. 


4 




.... 


298,0< »<•-<<• 


1 




.... 


3 






><),000 








0,000 


4 


44 






4 




.... 


►0,000 


4 


111 



mtffl foff pupils to make out for t heWU p lT M 
. lanetfl in tl ■•• — of tin- length <>f 

their day, and of their year. Observ. t) « between the 

nearest and most distant from the Sun of the Asteroids. 



Ifo- lira*. — Wk nn' U we may h<- ealhl to ae- 

. terms, tuck at 
. 
Mmtwede* if tit f/sesj on th' 

\n th Uaven* % an f ant as possiblt ; thai u ; 

plain' i in th' Uwi 

t would say that a child IUBBJ I ■ its placs 

on the map until it ha>l been first described. 

see thy work hat been In ths press, other Asteroids hsTt beta <U»- 



40 STUDY OF THE STAJRS. 

We now wish our learners to commence in earnest to learn 
from the actual Heavens the grand scheme which science has 
furnished for the foundation of Astronomical Geography, requir- 
ing nothing which the faithful scholar cannot accomplish. We 
will begin with the Northern Heavens. There the stars perform 
their circles around the Pole without ever setting, and hence 
they can be studied every clear evening of the year; and it 
better suits our purpose, because the upper Poles of our three 
systems range from the zenith north. The stars Merac and Dubhe, 
in the front of the Dipper, are the pointers, because they point to 
Cynosura, the Polar Star. Now observe the smallest star of the 
Dipper, Megrez, which joins the handle to the bowl. Look at it 
in connection with the Polar Star Cynosura. Measure the dis- 
tance between them with your eye in the Heavens and on the 
Celestial Globe. You will find by examining the globe that it 
is a little more than 30° ; but that is sufficiently accurate for our 
present purpose. Trace from Megrez to Cynosura, then carry 
your eye onward in the same direction, and at the same dis- 
tance (80°) you will see another bright star. This is Caph, in 
the Constellation Cassiopeia. These three stars, Megrez, Cyno- 
sura, and Caph, mark the place of the Equinoctial Colure, which 
is as the Meridian of the Heavens, — the principal secondary to 
the Equinoctial; from the Vernal half of which right ascension is 
reckoned.* 

To make our language precise it is necessary to consider this 
circle as divided at the Poles into two semicircular Colures, and 
we shall call that half circle which passes from Cynosura through 
Caph to its intersection with the Equator and Ecliptic at the Ver- 
nal Point — the Vernal Colure; and that semicircle which passes 
from Cynosura through Megrez to the Autumnal intersection of 
the same two great circles, the Autumnal Colure. Study this 
lesson thoroughly, both on the Celestial Globe and in the Heavens. 
It contains the key to our system of the study of the visible 
Heavens. We begin with the ever-present and well-known stars 
of the North. Learn as many Constellations, bright stars, and 
groups, which lie along the course of the Colures, as will make 
their places in the Heavens familiar. 

On the Terrestrial Globe study the Tropic of Capricorn as to 
the parts of the Earth through which it passes. What Oceans 
lie in this circle? What Seas? What continents? What 
countries ? What islands ? and what large cities in South 
America lie on or near it? Compare the quantity of land 
passed over by the two Tropics. What great difference do you 
find? 

* Neither Megrez nor Caph are exactly in the Colure, but sufficiently 60 for 
our purpose. 



CHAPTER IV. 

DEFIMTI 

-rxcnoN or Positions into ft and Movable. 

1, In punning the rabje i momical Geography, 

there are m Lions and explanationfl which an 

made necessary by the- imperfection of the human bent 
tice. We do n-'t dea who know m God 

thing m and 

who at the tame mom f all sph< 

in and without Our langv M meet theunder- 

Senaible 
i the Beavene; and 
whose na* lobe 

regard tl 1 as 

I thai ra 
be the direct line 
Earth, bat b> 

•'.iral ini; 1 in 

iiv, we shall dis- 
tinguish 

rir*t, BQcfa as M | 1 fixed in plate l»v 

[nator on the 

lo- 

place to a located ( >1 rtiead 

• 

Beinif f In vl. •-< God tc< 

•• langiin.- v , to 

whose un .imn 

iaeawenrn • - -t in sruith iu definitional What are the fint 
called I What the second I 

4* 



42 THE AXIS A FIXED LUTE. 

Circle, &c. The positions of the first class will be called 
Permanent Positions; those of the second, Movable 
Positions. 

3. The Earth's situation, with respect to the Sun, gives 
rise to certain determinate points and circles, and these 
are by nature Permanent Positions. The Axis of the 
Earth is the fundamental line, or Axis of Permanent 
Positions. It is by nature a Permanent Position; for 

Fig. T. Permanent Position*. 



although it is not a solid material line, yet the Earth as 
unchangeably revolves in its daily rotation around it, as if 
it were. It is represented on the Artificial Terrestrial 
Globe by the iron wire or rod on which it turns. The 
axis of the Earth being extended to the Celestial Sphere, 
becomes the Axis of the Heavens. The points where 
the Terrestrial Axis meets the Earth's surface are the 
Poles of the Earth. Those points where the Celestial 
Axis meets its own Sphere, are the Poles of the 
Heavens. That Celestial Pole which meets the Sphere 
in the Constellation Ursa Minor, or Little Bear, very near 

3. What gives rise to Permanent Positions ? What is remarked 
concerning their fundamental line or Axis ? What is the Axis 
of the Celestial Sphere ? What are the Poles of the Earth ? Of 
the Heavens ? 



HTMBH OF T1MK ANH * 43 

A star t. lied the NoMB Poir. of 

Tli. il Pole 

this ia : v ^ 1 JOB. The OOp 

.; Poles, 'I'll*' >tar 
There M DO I 
SI Star. 

Earth hat tl Circle the 

■. whose plane separatee tlie 
• ni and Southern Bemispheresi This 
I to the Celestial Sph< ribee 

This is ihe term by which As- 
tronomers des The 
plao • ;il we should learn to trao M W€ 

look out bj day <t by night upon the sky. It passes 

:i, the brightest and most 
beautiful in th.* firmament : and in ereiy latitude, tlie line 

- :n. in his da Dpon the 

Heavens. 

the 
of primary importano 
our science. 

to an equal dividing 
I Equinoctial, bom Equinox^ a word Bgnify- 
I t. refers to an equal dividii The 

. in one sense an imaginary line, as no 
wall will be found upon 
rerihdcsi by nature a 
real and a Permanent Position. It is the central circle of 
the B B tth, the interme- 

diate Hooted with 

the equal 

S. v. 1 1 < »f the Earth I 

icb t w I 

the Heavens? How should Wt lean t noctisl in 

the actual 

caotric circles, and of the names t 

In what sense i- isiiry lin«« I Hut what 

notwithstanding f Which are the fundamental Permanent 
ll 



44 



THE OBSEKTEK'S POSITIONS. 



6. Since the Movable Positions depend on the location 
of the First Observer, and since any point on the Earth's 
surface may be taken as his place, therefore all the ap- 
paratus of imaginary circles, lines, and points made in the 
science to accommodate man's limited view, are Movable ; 
and all depend on and move with that point of the Earth's 
surface assumed as the Place of the First Observer, and 
called the Upper Vertex. 



Fig. 8. Movable Positions. 

TM 

fbrtex 

OtensTPieJfoiizcn. 



ZENITH 

i ! 




Zcwer Vertex 

NADIR 

7. That place on the Earth on which the First Observer 
stands, and which we have called the Upper Vertex 
(see Fig. 8), has been incorrectly regarded as the Zenith ; 
but it is a point on the Terrestrial Sphere; and the Zenith 
is its corresponding point in the Heavens, and belongs 
solely to the Celestial Sphere. If we imagine a line, of 
which the Observer, as he stands, forms a part, descending 
from his feet downwards to the centre of the Earth, and 
from thence to the opposite surface, this, which we call 
the Line of the Observer, is a diameter of the Earth, — ■ 
and every diameter of a Sphere may become an Axis, 



6. How does it appear that all the Movable Positions depend 
on and move with the Upper Vertex ? — 7. How has the Ob- 
server's place been regarded ? What is the Zenith ? What is 
here meant by the Line of the Observer ? 



PC- KBDB.T RELATIVE. 45 

r8 Of Tin: IfoYABl I Poflm 

• the Upper \ nd its oppo- 

irhicb we nam.' the Lowkb Vmsm \. It' it !>.• oon- 
timied t<> the Heavens, it there becomes the Cdettial 

the Polt t/(/in>/ to the 

I tit <it corresponding t<> the 

\ \imi;. The Great Circle of the Ter- 

s of M"\ able Positions) 

es \i. .»r Kk m. EoRBoir, and the corresponding 

the Heavens i- the ( )ni tai i it 

Hemispheres into which these Horiaons 

th the H . .nil are the Uppi r "//'/ 

8. ms the Terrestrial and Celestial, 

-. and t<>r different 
r ilitr»-r»-nt portions of th.- Earth and 
ich of tli 
But, t<> meet our ooropre- 

i lori/.on t" -nit the plai 

vs.* mast move I the 

i on an Artificial < Hobe < , <>ni<l 

\. T!i. • we take 

assumed place a- that of 

. .it.- that role t<» which he 

number oi J t<> hi- latitude, and 

then jntil th.* place eh 

which represents th.- Meridian 
i>f the ( I Obeen er a ill be in 

i, and the wooden Horizon will be his 
tlobe on its Ax!-, v. 



■ 
I the ( »'■ 
■ the il'i 

•li. ir 

himself to be ? Suppose, ting a located 0/*ervcr ;. 

the Meridian, you then turn the globe on iU axiif 



46 THREE SPHERICAL SYSTEMS. 

once turn that Observer out of his place, and leave the 
wooden Horizon a thing without meaning. 

9. When we wish to understand the Earth's motion, 
as by turning once a day on her Axis, she presents her 
different sides successively to the Sun,— or when in her 
Planetary Orbit she revolves in space once a year around 
the Sun, then divesting ourselves of the notion of an abso- 
lute up and down, east and west, we must consider that 
ourself being first Observer, — these movable positions — 
Zenith, Nadir, and Horizon, will go with us wherever we 
go. A man may lose his fortune or his character, but his 
Zenith, and his Horizon — never. 

10. Uranography (from the Greek words Uranus, the 
Heavens, and grapho, to describe) signifies a description 
of the Heavens. It constitutes that portion of Astronomy 
with which Geography is most intimately connected. We 
have already shown two systems under the head of Per- 
manent and Movable Positions, the Axes of the two being 
the Earth's Axis, and the Observer's Line. A third system 
combines with these, as we bring in the study of Uran- 
ography, of which the Axis is the Axis of the Ecliptic, the 
Poles are the Poles of the Ecliptic, and the Great Circle 
is the Ecliptic itself. (See Fig, 1.) 

11. This system refers to appearances produced by the 
annual motion of the Earth around the Sun, by means 
of which the Sun appears to move around the Earth once 
in a year, keeping the same invariable track through 12 
of the Constellations. This track constitutes the first 
Great Circle of Uranography, and is the Ecliptic. The 
Positions of this system are by nature Permanent, and 
will be understood by studying them on the Celestial 
Globe. The Axis of the Ecliptic makes, with the Axis 
of the Earth's Sphere, an angle of 23^°, and of course 

9. In what cases must we seek to divest ourselves of the idea 
of an absolute up and down, east and west? — 10. "What is 
Uranography ? What two systems have been mentioned ? What 
third system is here introduced? — 11. To what does the third 
system refer ? What angle does its Axis make with the Earth's ? 
What angle is made by the two Great Circles ? Where are the 
Polar Circles and the Tropics drawn ? What may each of the three 
systems be called ? Of which two are the Positions Pennant* * 



;i:iMi:iAi. i.aihtm\ -17 

it Circles two Axea, the Ecliptic and 

r at tin- same an^lo. Through 

• > of th( m 11 tin Polar 

r. Touching the Eclip- 

firom the Equator, are drai n 

. . Of the three 

. having for its primary element the 

in of the Karth ; 

second, starting point the Upper 

01 and 

men! the Son's track 
in t. i faience to the two 

The 1 'oeitionfl of the 

rmanent ; of the second, Movable. 

12, A • importance to Geography is 

t Latitude are I 'ennanent 
m the Earth's sur- 
face i r, reckoned ia 

. < Jlobe tli** In 

i . lUatOT on 

een the Squat 

are in North Latitude and all 

h Pole in South /. 

- and minutes mentioned, 

♦ N S nth from 

trde on the Berth 

r about 69 English n. 

ire marked on the 

Bnaea M • .i its degre»> Uin<: t« »r conwni.-nn' nimi- 

1 1 * • - K«|iiat<»r to tin* I ' 
and Poleato the Equator. To ind 

the I the < rlobe, Bring the j 

imber al>«,\.' « ill snow, 
bom the Latin Mered 
The most i lea of a Jsfi 

11. What is Latitud. I Wl Bfthl To what U p 

degree of any Great Circle oo the Karth equal f 



48 TEREESTRIAL LONGITUDE. 

line, is such a line as would coincide precisely at noon 
with a shadow projected at the place of some Observer, 
by a perpendicular rod. Suppose such a Meridian -line to 
be extended North and South until its extremities pass 
into each Pole, the Circle thus produced would be the 
Terrestrial Meridian of that Observer. If its plane 
be extended to the Heavens, it is there his Celestial 
Meridian. His Zenith is in the upper point of this 
Celestial Meridian, and his Nadir in the lowest point of 
the opposite Semicircle. The Meridian, considered as a 
Circle, divides both Spheres into Eastern and Western 
Hemispheres. 

14. The Longitude of any place is the distance of its 
Meridian from some other fixed Meridian, measured in 
degrees and minutes on the Equator. The Meridian of 
any observer is not a permanent position, like the Equator ; 
nor is it so entirely movable as the Horizon, since it must 
always remain a Secondary of the Equator. It there- 
fore belongs not wholly to either of our two classes of 
definitions, but in part to both. A Meridian may coin- 
cide with a line or semicircle of Longitude, and it may be 
used as an Hour Circle. When some one Meridian is by 
common consent adopted as the first Meridian, and a 
system of semicircles of longitude accordingly made out, 
and, with parallels of latitude, placed on maps and globes, 
longitude is then to be regarded as equally permanent 
with latitude, — the Equator Being connected with both. 
Circles of Latitude are its parallels, and of Longitude its 
secondaries, — and both, accessories to the Earth's system. 

15. The Angle of the Latitude of any First Observer, 
or of his place of residence (which is the same thing), is 
the angle made at the centre of the Earth, by the Line of 

13. What is the most simple idea of a Meridian? How may 
a noon-line be extended to form the Observer's Terrestrial Me- 
ridian ? his Celestial Meridian ? Where are the Zenith and the 
Nadir ? Into what Hemispheres does the Meridian divide both 
the Spheres ? — 14. What is Longitude ? Does the Meridian 
belong to the Permanent or the Movable Positions ? For what 
may a Meridian be used? In what case do Meridians belong 
wholly to the Permanent Positions ? — 15. (Draw and explain the 
figure.) What is the angle of any Observer's Latitude? 



ABC 



tt 



that Observer, with tlio line of the fa] tho 

with thai M. I i lian. 

th€ M« ri'lian in- 

tween these two lines. And that Arc will 

s v In tin r it be taken on 

In the accom- 
pany r?ei ii 10° North. 




tho 

h t!.at angle a* the centre which is subtended by the 
atrial Arc <,/ {},, /. the 

What ta the etc of latitude to each 



50 REAL MOTION CAUSES APPARENT* 

part of the Earth's surface between the Observer and the 
Equator. The Celestial Arc of the Latitude is the Con- 
centric Arc on the Meridian intercepted between the Lice 
of the Observer and the Equinoctial. It subtends and is 
measured by the same angle as the Terrestrial Arc, and 
is likewise an Arc of 30°. In this figure there are eight 
angles at the centre ; of which four are equal to the Ob- 
server's Latitude, and the four alternates are equal to the 
complement of his Latitude (what it lacks of 90°), or 
(which is the same thing) to his co-latiiude. So that the 
elevation of the nearer Pole is always equal to the Lati- 
tude of the place. In the same way it may be shown 
that the elevation of the Equator is always equal to the 
co-latitude of a place. And since opposite Vertical 
Angles are equal, the depressed Pole is below the Hori- 
zon just as many degrees as the elevated Pole is above — 
viz., 30° — and its depression is equal to the Latitude. 
Thus, of the eight angles at the centre in this figure, 
four are of 30° equal to the Latitude, and the four alter- 
nates are of 60° equal to the co-latitude. 

16. If our Observer had been located at the Equator, 
the Equinoctial would in that case have passed directly 
over his head from East to West ; but if he moved North 
20°, the place over his own head always appearing up- 
permost, and his Horizon moving as he moves, it has 
appeared to him that the Heavens moved South, and that 
the Equinoctial and all the heavenly bodies had gone 20° 
in that direction. And the Northern Polar Star, which, 
while he lived under the Equator, was in his Northern 
Horizon, would, for every degree which his Horizon went 
below it, apparently rise one degree above. So, when he 
had advanced 20°, the Equinoctial would seem to him to 
have gone 20° to the South, and the North Polar Star to 
have risen 20° above his Northern Horizon. That is, the 
Permanent Positions, the Pole and the Equator, remain, 
while the Movable Positions, the Zenith and the Hori- 



15. "What is the complement of the Latitude of any Observer, 
or his co-latitude ? To what are the eight angles of the centre 
equal?— 16. Suppose the Observer located at the Equator! 



t ATinpr. wujsam i>. M 

tnge with th" of the I 

while t > him 

17. All maps are D the Situations of 

to Latitude and 

1 then putting them down in their proper. 

r, in order in plaoe, 

where it i> ; and he moat, when on 

raekless ocean, know exactly from day to day where 

in I. gitude h«' himself i< : else how 

'• in what direction to steer Ids ooaree .' The 

da by which obeerra- 

I m.-irii. 

» Mud hia Latitude, is thai of measuring th* 
altit'i B we have wen, ia 

always equal to th-- ' >h--r\.-r'> Liti:nd«\ . . Sinoe on the 

I 
. if his altitude, i 
in d. hia i the 

•li will 1 n er'a sferidi 

i from tin 

u d the aw of the Ife 
tad the point 

it is 
his oo-lati: 



EXSRCE 

In thp preo re teen thai there en three 

* : • us— lst»t th ; -Jd. that of the B 

ens; mprieed in tho 

science of Astronomical Oeoe 
eat, and r 

latitu 

with 

i will bi b •. repn 

tieel uses are the*- m nulwrv 

r»' ,k » m r • _r . i r d - No ;_- it i 'i and th«« science of Geography ? W hat 

:de of any 
*4»*«f Could it » . uking the Sun's altitu 



52 AXIS AND POLES OF THE ECLIPTIC* 

Globe, ana every Circle and Constellation will be in its proper 
place. Hereafter you may learn a more exact and scientific mode 
of elevating the Celestial Globe to represent the visible Heavens 
at any specified place and hour j but this will answer for the 
present purpose. 

Since the two Spheres, Celestial and Terrestrial, are concen- 
tric, and the Earth's is in their common centre, every Diameter of 
the Earth may be supposed to be extended, and thus to become an 
Axis of the Heavens, and to have its Celestial as well as Ter- 
restrial Poles ; and an Axis which has thus its Poles in the Heavens 
must of necessity pass through the centre of the Earth; but 
since only one — i. e., the Upper — Hemisphere, is visible to us, we 
can see only one Pole of each of our three Systems. But if we 
can see the place of one Celestial Pole in the sky, we shall know 
the direction of the Axis with which it connected, and learn by 
degrees how to find that part of its Great Circle which is within 
the visible Heavens. Seeing the place of the Pole, we shall 
know the direction of the Axis, because it is by definition a 
straight line from the Pole through the centre of the Earth. 

The Celestial Pole of the System of the Earth is at the North 
Star. If you stretch out your right arm directly towards it, 
your left directly opposite, your two arms will be in the line of 
this Axis, and your two hands will point to the North and South 
Poles. 

"We will next take the System of the Observer, because this is 
easier understood than the System of the Heavens. The Celes- 
tial Pole — yourself being First Observer — is over your head, 
and called the Zenith. The Axis of the Observer, or Mov- 
able Positions, is the line which includes your own person, and 
passes downwards through the centre of the Earth. 

The Axis of the System of the Heavens, of which the Ecliptic 
is the Great Circle, is of course perpendicular to the plane of 
that Great Circle. It makes an angle with the Earth's Axis of 
23 i degrees, and the place of the North Pole of this System, 
the only one ever visible to us, will be found on the Celestial 
Globe in the Constellation Draco, the Dragon, at the point where* 
the Winter half of the Solstitial Colure cuts the Arctic Circle. 
As no very bright star is near the North Ecliptic Pole, it is not 
easy to learn its exact place when you look at the Heavens with 
the naked eye. But you can attain a good idea of its position 
by considering that the Solstitial Colure intersects the Equinoc- 
tial Colure (whose position you know) at the North Pole of the 
Heavens ; or simply the North Pole. The Ecliptic Pole is nearer 
to the North Pole by 1° than either Megrez or Caph, and it is 
towards the same part of the Heavens as is the bright star Lyra. 
It is of great importance that you make yourself familiar with 
the Ecliptic Poles and Axis. Point towards its Poles, and your 
arms will be in the line of its Axis. 

On the Terrestrial Globe, learn the two Polar Circles. What 



VERlhAI. ( 53 

it each called I What is their d from the 

Equator? What oceans does each pass through! what oon- 

Whafl dinerenoa ii there between 

the r d regard to Hm quantity of land and 

which each passes I 



^ HAPTEB V. 



The B 9 there risuited. — Vertical Circles. — 

South. — The Prime 
• n l^t Link, exm.it at the 

l. 8 a by mat] 

living a 

- aa 

d it is si thai the whole 

surface of 3 lay be regarded as a M mi- 

ie on opposite rides of the 

one plane, the 

a complete ( Srcle, 

.-ill be a Gn i e of the 

s i oom- 
iu its 1 ' 

. the Te 

r and Lowet 
-ti.il hai 

. and 
I Poles, the Zenith and the Nadir. 

lea of a Bj 

:non Axis 
of a it are th< 

*tnn of Vcrticu 
** heloDir Movable rotiUooi I 

How does this appear I 

5* 



54 CELESTIAL BODIES LOCATE!?. 

8, The Line of the Observer and the Upper and Lowe? 
Vertex being the Axis and Poles of Movable Positions, 
to these, therefore, belong all Vertical Circles, the Prime 
Vertical being that which passes through the points East 
and West. The Great Circle of this Axis, is the Hori- 
zon ; any other Great Circle cutting this at right angles 
and passing through its Poles, is its Secondary. Every 
Vertical Circle is, therefore 7 a Secondary to the Horizon. 

4. Vertical Circles are of importance in the Celestial 
Sphere, as upon them is measured the position, which 
every heavenly body occupies, with respect to the First 
Observer. When the Zenith, Nadir, Horizon, Vertical 
Circle, &c, are mentioned, the place of an Observer ex- 
pressed or understood is always presupposed. 

5. The Altitude of a Heavenly Body is its number of 
degrees from the Horizon, measured by an arc of a Ver- 
tical Circle, The Zenith Distance is the complement 
of the Arc of Altitude. The Angles of Altitude and of 
Zenith Distance, are at the common centre of the two 
Spheres, and measured on arcs of Vertical Circles. The 
Azimuth of the body, must also be ascertained before its 
exact position at any specified time and place can be 
known. For if merely its altitude is mentioned, its posi- 
tion might be anywhere on a Circle of the same altitude 
parallel to the Horizon. The Azimuth decides where on 
such a Circle the body is ; it being the measure of its 
distance from the points North and South, either as taken 
on the Horizon from the Vertical Circle which passes 
through the heavenly body, or measured on any parallel 
to the Horizon in which it is found. The Amplitude of 
a heavenly body is the number of degrees of its rising 
and setting from the points East and West, 



3. What on the Earth and in the Heavens is the Great Circle 
of the Axis of Movable Positions ? What are Vertical Circles 
in respect to the Horizon, and why ?— 4. Why are Vertical Circles 
of importance in Astronomy ? In what cases are we to remem- 
ber that the location of a" First Observer is presupposed ? — 5. 
What is the Altitude of a heavenly body ? its Zenith distance ? 
What is said of the Angles of Altitude and Zenith distance if 
What is the Azimuth of a heavenly body ? the Amplitude ? 



55 

6. Xheaa definitions all 

ipposed located < >bserr< | they 

viy, bowerer, 
• -rtain parallel of 

I Bhon the reality of the d»- 

and Movable Poei- 

la iitu de ifoi a lti tud e * Fifty 

f * latitud d of a certain 

natural, determinate, and on- 
n : but ; • — what 

\V1,- •< . 1 1 riaofe 

\\^t\7aa\] Nothing, withoart an ( >1>- 
r, or Upper Verti i 
th, aod the Zenith of the i 
in ,: ,- 1 1- i\ ana Alti- 

••1 the H 
or — Altitude and other similar 
• 

Ponraa of the ( '"Uipaesv 
I V, w. \. s, 

He placed 

of both (Hobee, each being 

90 '. They an snbdirided 

utb- 

5° with the Cardinal Point*. 

hial an of - 

rtheaet, I. 

ie I rlohrs, <»r 

8. 

ial parti 

each truuieui, adjusted 

to g «h» p — having suspended on a 

6. 1 

I m I P b*1 is tbe 
•eteenodf — 8. * do these 

■ 
feet's Corapsesl 



58 TfiE MAGNETIC NEEDLE. 

Fig. 9.— Points of the Compass. Terrestrial, Vertical Circles, and Almacantara 




pivot within it the magnetic needle — a piece of mag- 
netized iron always pointing to the North Pole. The 
compass has each of the arcs of 22^° subdivided, and 
hence instead of 16, it has 32 points. Our artificial 
Globes have upon the inner rim of the Horizon, the same 
division of 32 points of the Compass. But, Geographical 
and Astronomical descriptions seldom need greater exact- 
ness than may be obtained by 16 points. 

9. Concerning the Points of the Compass, no little con- 
fusion exists in books and definitions. To see clearly the 
nature of the difficulty, let the Terrestrial Globe be recti- 
fied, say for New York. What from that city is the farthest 

8. "Where may you find 32 points of the Compass f 



not: nr. 

6 North ? It' \<>u answer me from the 

as of almost any book of Astronomical <Jeogj» 

raj>l D from W Dictionary, yOQ will say, 

\w Meridian <>( tie* < >!»-< r\ er at 
northern Doriion at 00° distance* 

What do J OH 

tind in \ It 10 die country be- 

ta, near bo the lake Baikal ; the 
the point named, h brkntsk. 
a, is Irkutsk due North from 
k! If balloons * mprored that atrarel- 

\ rth and South Vertical ( ' 

Irkutsk, would his whole 
N •• we! 

10. forward another question to be Bret 

r on the Barth, a pi 
. than the North r if you say that 

going a K rae would carry Ibe 

Irkutsk, then you 

S rth Latitude, tln-re is 

d of the Pole) i | 

by a number of degrees, equal 

ill those in South I 

re is a | me distance South of the 

the Earth 
are H nth point . the Me- 

N th Latitude ■ by definition 

DOOn, and North in the oppO- 

rae to all th< 
lode. A i th every Meridian on 

inch bo \n i 4 Erfcutsk, a> n ith 

The N then, the • 

in a 
balloon or anyotl. i could go direct from 

9. 'he fertile* 

Yot'k a bat 

furtlt. r <\ SSttlOO it tin;* Kr-.u^ht h.rw.inl f If \v.« 0m. ul 1 -iv 

that a r»T*on might tra\ i t!»«- w.i i 

*k, to what ftbfl are, 

, the Earth's . its! 



58 EAST AND WEST. 

New York to Irkutsk, his course would be North only 
until he arrived at the Pole, and thence from the Pole to 
Irkutsk it would be South. 

11. Nor is it merely with respect to the points North 
and South, that definitions disagree with facts ; for in no 
case, except when the Observer is located on the Equator, 
will the places on his Terrestrial Prime Vertical, as it 
descends to his Rational Horizon, be in reality East and 
West from his position. If he lives on the Equator, the 
plane of his Prime Vertical will coincide with that Great 
Circle, and all the places upon it will keep an equal dis- 
tance from each Pole ; and no line can be an East and 
West line, unless all the places upon it are. For the Poles 
are the extremes of North and South, and all Meridians 
are North and South lines ; and hence no line can be an 
East and West line which does not cross every Meridian 
at right angles, and at equal distances from both Poles. 
No lines but the Equator and its parallels of latitude do 
this ; and as no parallel of latitude is a Great Circle, and 
the Equator is, it follows that the Prime Vertical of no 
Observer on the Earth can coincide with an East and 
West line, except the inhabitant of the Equator. It fol- 
lows, also, that all lines of latitude are due East and West 
courses. 

12. For illustration, we will place the Observer of New 
York at the Upper Vertex, and see where his Prime Ver- 
tical will cut his Rational Horizon. Of course it will be 
at the intersection of the Equator with the Horizon ; for 
that is always the point East, whichever Pole you elevate, 
and for whatever latitude. Here we find Lower Guinea, 
an equatorial country, which no one will say is in an 
East course from New York. On the contrary, all must 

10. How, then, is the question to be decided concerning the 
Point of Compass followed in going on a direct line from New 
York to Irkutsk? — 11. In what ease will the Observer's Prime 
Vertical indicate, as it descends to his Rational Horizon, a 
true East and West course ? How may it be proved, that but 
in one case will the Prime Vertical show (at the distance of 
the Rational Horizon) a true East and West direction ? What, 
besides the Equator, are due East and West lines? — 12. What 
^lustration is given I 



Tin 59 

see th.it it cannot be - the Vertical Circle, which 

] «»rk t<> t hat plaoe, i*ut^ all 
it passes at ohli.jne angles, going 

er and farther from the North role, until at the 
has increased 40°, a number just 
ititude of New Fork 

the short, st distance between any 

v definition, an are ol 

:' latitude are never < heat ( 81 

then, thai ■ due ind Wert comfee 

es on the same latitude is not the shortest, 

r. The greater the distance 60m 

gator would lose by 

Bah . who should follow a line of lati- 

-• npon the same paralleL 
1 \. To make tl rre where the line of W« 

io°ctos< • between America and 

f altitude and lay 
it fr -md 

muM in 

and how 1 • most 1- I he sail from 

• r on th' latitude 

in, the same inn. miles nearer the 

.i-.-r the P 

1:.. Since si] 

. any tWO pi 

found bj _■ "ii the same 

Men-. I d w hid) the n Bails, betwei d 

any I called I 

ir>. 
bet** 

is u-soful to 1 ' o <,._rraj.l 

well as I and the sim] d in <>nr 

13. What i* 
When roar a doe Ea*t ami Weit line tx 

•w a east 
trat< 

>utb cour»e I What U Uie navigators oblique line called f 



60 THE COMMON CENTKE. 

case, and perhaps in that of the navigator, might be, to 
make an arc of a Vertical Circle, by putting one of the 
places in the Upper Vertex, and by carrying the quad- 
rant of altitude from the Zenith to the Horizon, so as to 
intercept the other. The number of degrees' distance 
will be shown by the intercepted arc, which, multiplied 
by 69, will show the number of English miles.* 

17. Vertical Circles would, if the Earth were a plane 
stretched out like a map on Mercator's projection, truly 
indicate the points of Compass in every latitude ; and so 
far as the Observer's Sensible Horizon is a plane tangent 
to the earth, so far, and no farther, will Vertical Circles 
truly indicate all his points of Compass on its surface, 

18. In the light of this subject we see the indispensable 
necessity of distinguishing the Permanent from the Mov- 
able Positions. Especially must this distinction be borne 
in mind as we look at night upon the Northern Heavens, 
There the two systems are almost entirely distinct ; and 
indeed, as we have seen, in one case they are opposite : 
the same line, which referred to the Movable System is 
North, being found, as regards the Permanent, to be 
South. 



EXERCISES. 

The Axes and Poles of our three Systems being determined, 
let us now look to the visible heavens, and see what there we 
can find respecting their three Great Circles. And here our sub- 
ject, so perfectly simple in the beginning, begins to grow some- 
what complicated. For we are to consider, not only that each 
of these three Great Circles has the centre of its plane cut at 
right angles by its Axis, and that each is ever at 90° distance 
from its Poles, but, furthermore, how they intersect each other. 
The centre of the Earth is the common centre of the three. 
The connection of the System of the Earth with that of the 
Observer is regulated by the Observer's latitude, and is therefore 

* The number is expressly sanctioned by Sir John HerscheL 

16. What is the best method of measuring places on the arti- 
ficial Globe ? — 17. In what supposed case would Vertical Circles 
truly represent the points of Compass ? In what real case do 
they rightly indicate those points? — 18. What are the concluding 
remarks of the chapter ? 



Tin: vkkxal i ILL v<>\^ 61 

not deten lo the connection of the two 

rmanenl Positions, 
they are by tjH ' wmurying angle ol inclin.it i. 

wo Axes, v. . J°, Tho two (iiv.it Cii' 

ai the sum- ingle 
angl< the Sphere, which, of all 

- drawn the only one 

t" t»<»th tin- Keliptic and tin- Ktjui- 

It p—eoi through 
both ' irth md Um Polee ol the Ecliptic, and 

cuts both the ( ' the two op] into where tneir dis- 

tance from each othec II the pp 

will aj^ain r- I -tars in the North, once they are 

i of our nights, We will, for conve- 
nience of divi-lo v. of the tu each 
into * The i : through the Summit 
5o/j.'. '•■int in 8pac$ where the Bon ap- 
penrt at - will ceil 
summer C . which noeeei 

tor Sol*tit The 

Cardinal Point* of I important 

wfcaM pOM' -: .'. i !•«• t'ir-t and ri.'-t thoroughly iinjr. --. d 

jpon \ ernaJ haJ 

pnsi»i through it. 

-'i9eee> 
in the r«-ar. It lore through which 

h passca, and is twice as many i ipb, M Oeph Li 

■ 
Eodeavor to identify tl n the Hem 

a> in it, u tl/ 

mark able Mar- in tin* lead ..f t 

; tli.' 
BOOOnd n:.i.- . ■ Ari'tia ai -1 Afrtartin, which we may learn to 

Boll, m known 
to all, by • ip in it ii 

called tne II y ode* ; ai he great si iraw. 

On 
the Oceans an : '«, Seas, Great Bay- 

tries of the Toaam Zonk. 



CHAPTER VI. 

Equinoctial Points in Space. — Equinoxes in Time. — Defini- 
tions. — Earth, Diurnal Rotation. 

1. The Vernal Equinoctial Point is of paramount 
importance. As we shall have frequent occasion to men- 
tion it, as also its opposite, the Autumnal Equinoctial 
Point, we shall sometimes abbreviate and call the first the 
Vernal Point, and the second the Autumnal Point ; but 
we shall on no account call them Equinoxes, for there is 
an important distinction to be kept constantly in view : 
the Equinoxes belong only to Time, whereas the Equinoc- 
tial Points belong solely to Place. They are the points 
where the Ecliptic intersects the Equinoctial Line, or 
Equinoctial — a name by which astronomers distinguish 
the Equator of the Heavens. The time of the year when 
the Sun appears in these Points, is the Equinoxes. The 
time when he is in the Vernal Point is the Vernal 
Equinox, and the time when he is in the Autumnal Point 
is the Autumnal Equinox ; but the places, we repeat, 
where the Sun is at these times are the Equinoctial 
Points, and may be seen in the visible Heavens. Though 
these two Points thus far require a common definition, 
yet the Vernal Point, being that from which Celestial 
reckoning begins, is of superior importance. In Time, 
also, although the two Equinoxes are alike in respect, 
that when the Sun is in either, there is " equal night," 
yet the Vernal being at the beginning of the year, takes 
precedence of the Autumnal. 

2. The Declination of a Heavenly Body is its dis- 

Chapter VI. — 1. "What one Point in the Heavens is of para- 
mount importance? What distinction is there between Equi- 
noxes and Equinoctial Points ? Which Point in Space takes 
precedence, and why ? Which Point in Time takes precedence, 
the Vernal Equinox or the Autumnal Equinox, and why ? 



NATION. 

ctioZ, me aiur ed on 

t1t< Vi mad h'llf ' i>u- 

nortial ( dly the same definitioi 

le, but in Astronomy At Latitud 

any I from the K>/u 

'I'll.' /. 
Body is its </ s ipde 

tchich passes thron'jJi 

on t! stance from the same point 

— that ia, ired on the Eqni- 

Both Longitude 
and KMunoa ire reckoned in tin* otdef of the 

round to the same point — 

to 360°. This point, to often mentioned *s die 

fir*t of same a- rarinoctisj 

detennin st point in Bj 

it the place in tl which the Sun i> teen <»n 

. y. m begin 
the mon. rnsj 

Ion 

3. Young ]• simplicity of 

messurem* m in Ihe Celestial M 
are natur . by Latitude and Lon- 

otoned fimfl linoctisj an-1 from a flxed 

Sec*- fully answered the purpose in 

Astronomy as well a.- 

why to the Astronomer tl nst be t 

from which to reckon in the I : and of 

course if Celestial from the 

Celestial Loi._ 

of ti. chosen in which the Sun 

appears at the time when : year begins. 



the Declin.v 
nition of Oecwi aii esaentially like I • stial 

Longitude J What beaidea in r 
what order U Lonpr 

i each is r 
Wtflt 

Venn' f naturally inflgtsttd 

to the learner f What replj u made to thii question f 



64 C. LONG. AND RIGHT ASCENSION. 

4. But after Celestial Latitude and Longitude had been 
thus established, would not Declination and Right Ascen- 
sion have been spared ? We answer, they could not ; for 
Astronomical Geography indispensably requires a Celes- 
tial measure answering to Geographical Latitude ; and 
such is Declination. The necessity of this will be fully 
apparent as we proceed ; and since this was necessary, a 
corresponding measure on a Secondary of the Equinoctial 
was of course necessary also. The first Secondary of the 
Equinoctial, which is that where the Sun is when the 
Astronomical year begins, is the Vernal Colure ; and from 
that Right Ascension, answering to Terrestrial Longitude, 
as before stated, is reckoned. 

5. But why, the student who reads without examining 
the Celestial Globe, may ask, why, since the Sun is at the 
commencement of the Astronomical year in the first 
Secondaries both of the Ecliptic and the Equinoctial, why 
are not these the same ? and since Right Ascension and 
Celestial Longitude are both reckoned from the same 
Point (the Vernal Equinoctial Point) round the whole 
360° to the same Point again, why are they not the 
same ? Because, as the Ecliptic, with its principal Sec- 
ondary the First of Aries, intersects at this Point the 
Equinoctial with its principal Secondary, the Vernal 
Colure ; yet, going from this Point, these four Circles 
diverge — the two Primaries at an angle of 23^°, and the 
two Secondaries, of course, at the same angle. All 
Circles of Celestial Longitude being at right angles to the 
Ecliptic, meet in its Poles, and all Circles of Right As- 
cension being at right angles with the Equinoctial, meet 
in its Poles — i. e., the Poles of the Earth. No Circle of 
Celestial Longitude is coincident with Right Ascension, 
except the Solstitial Colure. 

6. Circles imagined to be drawn around the Observer's 
place, as a centre, are called Almacantar Circles. The 

4. What query here concerns Declination and Right Ascension ? 
How is this query answered ? — 5. Examine the Celestial Globe, 
and explain in what respect Celestial Longitude and Right 
Ascension are alike, and in what respects they differ ? — 6. What 
is said of Almacantar Circles, both Terrestrial and Celestial? 



: 
1 
the Moi ible I \ - ; ;:"':-. Hn ] 
\/imuth Circles, and < Circles of Altitude* 
^nation they belong Bolely to the Celestial 
hall take- the liberty to transfer th£b, by 
tan, OF Alma»'antar GildeS, t<» tli. 1 

Tern- S need them in an important 

Geographical problem. They have heretofore been need 
ire the H rees ; bat we intend to 

use them for I m of measuring the Earth 

in mi 

in view this design, we are especially d< 
rous that our learnen should folly understand these 
• lea. It' we *li"ul<l faney an immense pair of com- 
passes to hart 'ill, and the other 

itial 
. 

•urso 
60° from the Horizon. It' t; . — •*, tin < 

rith 60°, 1 Almacantar ( 

would be ing all Verti from 

the Zenith, a* I 80° from the Hanson. E 

• drawn I • 60° 

of Altitude and 30° oi d all those on 

the secon 30° of Altitude and 1 Eenith 

8. Again: suppose ' >mpa— • s <t dividers, 

bro\i_ rth, and the stationary 

ng place- 1 p •■•» imaginary 

: be « 1 r. i 

trial 

d these, '• old make three equal 

gradations of terror. 

6. To which 

belong f 

Waal •:•• do< * Um author -1« -un t.- make of 'I', m--tn.il Alma- 
can tars f— 

rcl^*, b*ginnin. ivewf — 8. 

Make a »imiU: nacantart I 



66 CELESTIAL MOTION. 

9. In Astronomy, the points East and West refer to 
the order of the Twelve Signs of the Ecliptic, which are 
numbered from West to East. This is the course of the 
Earth in her orbit, and of the Sun in the Ecliptic. If 
any heavenly body moves in this direction, its course is 
said fb be direct ; if it does not move, stationary ; if it 
moves contrary to the order of the Signs, retrograde. 
But, says the young student, do I not see all the Heav- 
enly Bodies moving every day from East to West ? Are 
their motions retrograde ? If not, what are ? No ; their 
motions are not all retrograde. Unless they are moving 
with respect to each other, they are regarded as eternally 
at rest. Thus with respect to the fixed stars, not- 
withstanding they appear with the whole Heavens to re- 
volve once in 24 hours about the Earth from East to 
West. Their apparent Western course is caused by 
the real motion of the Earth on its Axis in the contrary 
direction. But it is the motion of the bodies of the 
Solar System, regarded in reference to the fixed stars, to 
which the terms, direct, stationary, and retrograde, are 
applied. 

10. The motions of those Planets whose Orbits are ex- 
terior to that of the Earth, and which are therefore called 
the Exterior Planets, are always direct. That of the In- 
terior Planets, Mercury and Venus, would always appear 
direct if seen from the heliocentric position — that is, from 
the Sun ; but when seen from the geocentric position — 
that is, from the Earth — they are direct only when the 
Planets are beyond the Sun. When moving between the 
Earth and the Sun, their motion is retrograde ; and when 
either advancing or retreating they are on the sides of 



6. What is to be understood by the terms East and "West, as 
used in Astronomy ? Explain the terms direct, stationary, and 
retrograde. What inquiries may here present themselves to a 
young student ? What reply does your author make ? — 10. What 
is here said concerning the motions of the Exterior Planets and 
of the Interior Planets ? What position would a fancied Observer, 
standing on the Sun, be said to occupy ? What position is that 
of the Observer on the Earth said to be ? (In Greek, Helios is 
the Sun, and ge the Earth.) 



paii.y aiti*akaniT> — MOBHIHO. » ; 7 

where tai the Earth would i 

11 Ktinial motion, the extended pi 

of t: ri tntly moring for- 

I in the ^ B Ml to West, and 

tli«' mean time, that the 

whoi ] in an opposite direction. Se 

ruth, that the Sun is stationary 

and jr, than does BOme child, upon a ta>t->ail- 

it. that tl • which t& - n iwiftly 

past bin . ■ lightrhome on the shore, W 

;-»s, tho illusion would bxv 

n of the o And 

so wil Son fly peat him, but 

9 
in, by the use of the Tew >be and 

a sta* the hud hich 

we are affected by a diurn itioo of the Earth, 

shoi, about it- thin 

i<x)sing the location of 
g our place to the 
th its tram. 4 , so as to 
lative position with reg 
I fiaon daring the whole revolution, < >ur | 
will thus continue to ap] \, — 

our Horizon bein_: nt. 

Lei n fancy our j to be somewhere on 

the 1 ee <»ur time to be six o'clock in the 

mor* 10.) The Sun's disk is dow cot by 

our East I thus he appears to us to be 

g as we U*£pn our diurnal 
moves, it carries us V ist, making the whole 

Palest i si 8j here appear to m-v.-. as if it revolved on the 

. II. -u •, 

How is tbe fact illustrated, tl -iry, 

teart to the Obserrer to move- I we 

raining an idea from the Terrestri I 
h we are affected by a diurnal revolution ot 
Earth' — 13. Draw on the blackboard. I 10 the repre- 

tea t a t ioo ol ■ Morning," and describe from Uk 




68 



MORN- 
ING. 



WEST 



Fig. 10.— Diurnal Eotatlon. 
ZEN { ITH 



CAST 




^ 



EVE- 
NING. 



«va 



NAbld 




8 



uiqvN 



^ 



ism 



H1IW32 



MID- 
NIGHT. 








^ 



^ 



AND IVJUUHk 09 

whilo the artificial Terrestrial Globe lias its true motion 

I ita A\> from Weal to Bast, the artificial Celestial 

^ the Eeav* os q pear to mov0 

1 ; have mored from Wart to Bast, how 

will our 1 I to move with regard to 

Sun ? As wo move towards the Sun in going to the 

. -t.int from as 

— wiO sink beneath; — thai glorious body always keeping 

e — ><> thai when we bare moved an hour, the 

will Ik? an hour high, and our time will be seven 

•k in the morning. When we have moved two 

boon, Sun will be two hours above our Borixon; 

or, rather, thai will have sunk two boms beneath it. and 

our time will be eighl o'clock, a. m.* When we bave 

..ill haw gone through one quarter 

of o- and the Bun will have ap* 

Eircuil through the 
eavens ; our 11 riaon in I having proceeded 90° 

s the Wi b( hai ii g advanced 90° 
ith, and it is N 
i 

■ A"- 
l :». Bui th< i >n her A 

mom ikes her. As we move, our 

and our Eastern 

Sun, while he appears to us to be going 
in a cool i, and declining towards the W 

•' three hours, it o'clock, p, m. At 

her quart is corn- 

western Horizon i 

• rial l [< h 
►n, have all puu- 

M, Ante- Meridian— i. 
ian, a: 

14 In the wme manner draw I 

raw and deaenbe in like 
maimer the change : s to Evening. 



70 FROM EVENING TO MORNING. 

with us — since our feet have been always downwards 
towards the centre of the Earth, and our heads always 
upwards from that centre — we have not naturally the idea 
that we have moved at all ; but while in reality we have 
been going East from the Sun, the Sun seems to have 
moved West from us. From sundown to Midnight we 
have moved through another quarter of our daily Circle. 
Our heads pointed successively, as we moved, towards 
various constellations of beautiful stars. When our 
clock, which still to our view keeps its upright position, 
shall strike twelve, our heads will point in a direction the 
opposite of that in which they were at noon, but our 
Zenith has still kept over our heads, and our Horizon 
been around us. We are still attracted to the earth, just 
as we were then, and are not sensible that we have moved 
at all ; but we have only fancied that since Noon the Sun 
has declined from the Zenith to the Western Horizon, 
and the stars moved from the Eastern Horizon 90° to the 
Meridian. 

17. From Midnight to Morning we now move during 
another six hours ; but we still occupy the Observer's 
place in the vertex of the Upper Hemisphere, and we 
fancy, as we are turning towards the Sun, that the stars 
of the Zenith are descending towards their setting in the 
West. As the Eastern edge of the Horizon is turning 
towards the bright " Eye of the World," we begin to en- 
joy his warmth and dawning light ; the mountain tops 
are illumined, and at length, at six o'clock in the morning, 
we behold 

" The Powerful king of day, rejoicing in the East." 

18. We are now at the same point at which we began 
our diurnal revolution. Having been on the Equator, we 
have moved nearly 25,000 miles, — the greatest measure 
of the Earth's circumference. But since we have changed 
neither our place on the Earth, nor our Zenith, we have 

16. From Evening to Midnight. — 17. From Midnight to Morn- 
ing again. — 18. How many miles must we, as Observers, have 
moved in a day ? Why, in making this Circuit, have we been 
insensible to any motion of our own ? 



B& 71 

nceit that th«^ middle o( the Earth ta 
re we are, and the t<>j» of the Searena directly 
our We have not 1 sihle thai 

. although ire have gone mora than a thou- 
sand mile* as hoar; 1 ait we hare Banded that the Sun 

ocupied with making immense 
ial benefit, and to wre our little 
Earth th 



u possible, to enable our pupil*, as they 

iblfl to locate them from obeerring 

the ■ they look 

■ j nisi t ion, 10 DOTOl f<>r :i 

jiit fully preparing the way far 
t be mad< . bat 

I nly 

I from and on the 

i\ of An- th.' 

.:i. -<Mi.il, Celestial latitude 
and 1 coincide with TerresrriaL 

But n <!<«, in the Oelestia] 

trial latitude and longitude; tx 

• t ial at»<l it- halfsecondarT, 

- fr<>ni Longitude, m 

goinir way only, but quite muiid the 

It i« to I D that we "hall now 

. wr lo.»k out upon the Marry 
heavt-n-. T 'rial hall" 00 whiofa Wt 

•tan*' I hand oorthwafd and upward ton 

ki te the I 

by as many degrees aa j 

quite r«uod the Karth, though only half of it can at OOO 
aeen abov.- 

leavor to conceive of th- liar Oolun 

ce aecondary to 
at right angiea in the Polea each di\ i i I h ok 

how tbetie Col urea are makir 
North Pole, extending South and aeparatiog in I ions — 



72 STUDY OF THE CELESTIAL CIRCLES. 

keeping, of course, 90° apart — crossing the Equinoctial at right 
angles — then beginning to converge until they meet at the South 
Pole, in the same manner as at the North. If you find this 
difficult from the mere examination of the Heavens, study the 
Celestial Globe. 

You know that from the Equinoctial to the Pole is 90°, and 
you have begun to learn to measure distances in the Heavens by 
the eye. Then, knowing where are the Equinoctial and the 
Poles, you will more and more learn to decide by the eye about 
the degree of distance North or South from that Circle. This is 
understood as Declination. But for Right Ascension, study the 
four Colures. The one through which Caph passes has no Right 
Ascension ; but it is that Meridian from which Right Ascension 
is reckoned. Then go a quarter round (90°) from West to East, 
and there is the Summer Colure, having 90° of Right Ascension. 
Then the Autumnal Colure, with 180°. Then comes the Winter 
Colure, 270° ; and, lastly, the whole Circle is completed at the 
same Vernal Colure from which the reckoning begins. On the 
East side of this Colure is 0° ; on the West side is 360°. With 
these Circles and numbers remembered, the intelligent student 
will be able to judge, with general correctness, of the Declina- 
tion and Right Ascension of any heavenly body ; and further 
exercises will improve him, whenever he pursues them, either on 
the Globe or on the face of the sky. 

What is the Declination and Right Ascension of Megrez ? of 
Arcturus ? of Capella ? of Procyon ? of Sirius ? of Spica Vir- 
ginis ? of Caph ? of Cor Leonis, or the Lion's Heart ? 

On the Terrestrial Globe, study the Northern Temperate Zone. 
What portions or divisions of water, oceans, seas, bays, and gulfs, 
does it contain ? What divisions of land, continents, countries, 
and islands, and what great cities, are in this Zone ? 



CHAPTER VII. 

Signs of the Ecliptic. — Retrocession of the Equinoctial 
Points caused by the Precession of the Equinoxes. — An- 
nual Revolution of the Earth in her Orbit. — Apparent 
Motion of the Sun in the Ecliptic illustrated by a 
Father's Expedient to teach his Son. 

1. With the two systems, which we have denomi- 
nated those of the Earth and the Observer, we have in 
connection, as we must recollect, a third, whose primary 
element being the Ecliptic, we have denominated it the 



Till 

twelve l 
road, through 

— <•> in his nppmvnt annual O0UIS6), With 

r the .-an. oon- 

s t .or the Ham; which - Bun enten 

B , or the Bull ; which Biga the 

m ; which Sign the Boo 
TTie I 3 i hieh Sign the Sun 

: which Sign th.- Bun enten 

a ; whk h Bigo Um San 

- i the Sun 

. the Sun 

«rhi< h Sign 

an; which 

thus divided 
ch, and these tv. 
to the I * 
r emblem. ] 

in t) ami 

upn V II — i 

Ube Zodiac * (J/alv on f/ ( ^ hJurkh'xirdtJu tof/t* Signs.) Mention 

Can* • 

lattons of the ftamc name DOW tor 

nj baa be« MOB m I bat, what haa 

•here Utn >:, Sj Mi f 

7 



74 PKECESSION AND RETROCESSION. 

Constellations were going on together ; but now, by the 
Precession of the Equinoxes, there has been a Retroces- 
sion of the Equinoctial Points ; so that the Signs are 
30° behind the Constellations ; and in the Heavens, at 
the Vernal Equinoctial Point, where together was the 
first Sign and the first Constellation, we now find the first 
Sign ( <p ), Aries, and the twelfth Constellation, Pisces. 

3. This subject has been, as we conceive, perplexed by 
a lack of precision in language, arising from a want of 
proper distinctions. The Equinoxes (equal-nights), it will 
be recollected, belong to Time, and the Equinoctial Points 
to Space — they being the places where the Sun appears 
at the time of the Equinoxes. By the advance of the 
time of the'Equinoxes a few minutes every year, the place 
where the Sun had appeared in the Ecliptic is not quite 
reached. But this place must be in the Equinoctial ; and 
thus it happens that while there is a Precession of the 
Equinoxes, there is a movement of the Ecliptic upon the 
Equinoctial, and a corresponding Retrocession of the 
Equinoctial Points, which, in 2000 years, has amounted 
to 30°. 

4. Of course the Pole of the Ecliptic has the same 
motion, with respect to the Pole of the Earth, as the two 
Great Circles of the same systems have ; and so also 
must all the Circles connected with each. Any degree of 
Celestial Longitude will not, therefore, indicate the same 
position of the same stars now as formerly. 

5. The grand phenomena of the daily apparent motion 
of all the heavenly bodies, in consequence of the Earth's 
rotation on her axis, is so striking and sublime, that it 
dazzles our vision, and hinders our perceiving at first, what 
is in itself more vast — the yearly motion of our planets. 
The annual path which the Earth describes in moving 
around the Sun we term simply the Earth's Orbit. In 
form it is an ellipse, though not varying greatly from a 
circle. An ellipse has a longer and a shorter diameter, 

3. How is the term Equinoxes used ? Explain how Time pre- 
cedes and Space retrocecics. — 4. What is said of the Poles of the 
Ecliptic ? — 5. What is said of the Earth's annual path around the 
Sun ? What is an ellipse ? 




n 



an«l two foci) in one of which is the Sun's place. Th« 

is somctim-s. but maintain, improp- 

iptic ifl n<>t from 

cllipsr, b *i to "V 

id.'. 

wliirh, to an 

Sun, though at rati, apj 

S8 the Earth j- in an Oppo- 

I I 

ens. f f> inn plans 

Earth'* Orbii tm fast oi At bffer i But 

• 

reacli'. annual path. 

6. ' (rf the 

CeU : the bititadfl of * •nly bod» 

I from it. 'I atrial 

the :: iritfa the oommoo 

# Eq Bttli confusion oriftl in I 

6. Why || it i uM W ip it to r.iU ti. 

booed fr- 
and wbj 1 How m .v U 



76 the sun's apparent motion. 

7. We once heard a learner say : " I see that there is a 
diurnal motion of the heavenly bodies to be accounted 
for ; but in regard to an annual revolution, one day seems 
to me like another ; and I do not see any evidence that 
there is a yearly motion." We may, however, be con- 
vinced, by observation, that there is a circuit made in the 
Heavens, which is completed in a year. Indeed, it is from 
its completion that we obtain the idea of a year. If we 
take some specified hour in the evening, as nine o'clock, 
and observe some one star, as Aldebaran in Taurus, we 
shall find it changing its position relatively to the Sun at 
the rate of 30° each month. Or if we keep our attention 
fixed to our Celestial Meridian, at some one hour when the 
stars are visible, we shall perceive in the course of the 
year that all the Constellations — not only those of the 
Zodiac, but all in our visible Heavens — will (advancing 
from the East) come each in its turn to the Meridian ; 
and this proves that a yearly revolution of the Sun in 
reference to the fixed stars, either real or apparent, does 
actually take place. 

8. The knowledge gained by Astronomy of the mo- 
tions of the heavenly bodies, makes it certain that it is 
not the Sun which really moves through this vast circuit 
of the Ecliptic, but that our own planet, by changing her 
place as she moves through her comparatively little orbit, 
makes the Sun appear thus to move. Hereafter, should 

raphy from the indiscriminate use of the terms Ecliptic and 
Earth's Orbit And the confusion becomes worse confounded 
when the signs which solely belong to a Great Circle of the 
Heavens are placed upon an Artificial Terrestrial Globe for 
learners. To the young mind, the Earth seems tasked to carry 
her annual journey on her back, with all the Constellations of 
the Zodiac. Mr. Townsend, the author of an ingenious " Mechan- 
ical Zodiac," seems to have had a just appreciation of this abuse 
of the human understanding, when he says, "The subject is to 
most minds an inextricable confusion? 

1. "What was said by a learner? But how may we know 
from observation that a yearly revolution of the Sun, either ap- 
parent or real, does actually take place ?— 8. Is the Sun's motion 
real or only apparent ? What causes the Sun to appear to 
move? 



A PfWtBUJTT DEMONBTBaTED. 77 

us science of Astronomy, you will 
: the truth of this great fact But 
. am the real motion of the Earth round the 
Sun in an ellipse make the Sun appear to move in a 
ad the Earth, and through these im- 
at group* of fixed stars ? 
a little picture* of i small island, in a. 
lak.' >n all sides by various objects. The 

in the centre is the residence of Mr. Teach- 
bis gentleman's young son, Charles* was much 
he could not understand how the Sun, 
standing still in the Heavens, should, by the Earth's 
rod him, Beem to make a yearly circuit 
ds of the Zodiac 
10. ther having become, by previous industry 

. a man of wealth and leisure, thought that 
1 be well spent in encouraging 
. Bo he caused 
to h rod, something like a 

great Solar-Lamp, I Sun. Be lights it, 

nn«l then at the h m into s boat, 

otion to the motion of the 

istantly fixed on the mock- 

• 1. II.' then rows him quietly 

roun«l the island, making his course, not in a circle, but in 

an alii] 

li. mind to the subject, and 

not thinking of tl \ perceives that as 

he ss -sun appears to him to m 

m a ; and, as he k 
:. the lamp-sun appeal 
dirt< ■ • En m. 1 ition Dear the t«»<'t 

Iffr, T, and 

hereafter 
to b- ubd of the 

at. 

V-l 

ifOTl 



INTRICATE SUBJ ED. <0 

he seoi the lamp n if it 
were in ind aa he moves, it m 

apparently going round the circuit the same way,* teeming 

\ ar, the mansion, and then* 
the - , and bo on until, when he had oom- 

1 his lit r >und the mimic-sun, that had 

i oomplete circle, and oome to the i 

is when he set outf Ee then perfectly 
that by the illusion of his right the lamp-son 

ha<l I to him I t and very ' 

. he had sailed around it, in a small ellipse* 
Win n the mansion 

and ■ amed to | 

untain j hut to his vision the track was 
as near a- poaite pari of it.** course, it ap- 

parently passed over the mansi 

led Chailes to form a oinle 
paper, makii 80 ' each, and 

1 the lake, over which 

«, into tn 

. 

ostdUations of his 

called the constellation Statue, 

noond the constellation Mansion, the third Summer- 

i on. The father and Bon at many a twilight 

I th«*ir lit - to clear up 

( mi one evening the 

• was to show the youthful learner how sailing in 

an e lock-sun in one of the foci, the ap- 

oonatalla> 
tions would be greater than in others, though the motion 

# That j*. i* apparently goes ore r ame euc- 

- 
f Only a qure n on the picture, M<>ro 

lan 90° cannot well be taken in by tl 



11. OQt ft litti 

for hU a* i clre 

iittlc zodiac through which hi* mimic ecliptic 
W 



80 SIMULTANEOUS MOTIONS* 

was equable. Another point which was made clear was — 
how, since the Sun, hiding the stars, is never seen among 
them, can we know that he is in a certain constellation ? 
Referring to the place of the little Ecliptic, Mr. Teachwell 
carried Charles around the circuit, with his back to the 
sun. Seeing what constellation his own little earth-boat 
was in, he could know that of the sun, because it was 
always in the opposite sign in the Ecliptic. 

1 3. One evening, after our little traveller had become quite 
familiar with the idea that his own real motion produced 
an apparent motion in an imaginary line made by a 
mock-sun through objects which, though at different dis- 
tances, all seemed at the same, his father took him in the 
boat when the hour was later, and there was no light 
except what proceeded from the lamp, which was made 
very brilliant. Then as he rowed his son around the 
little island, he made him turn on his feet round and 
round the same way that he was rowing him. This was 
to represent the Earth's daily motion on her Axis, while 
at the same time she is carried around the Sun. His 
father told him to imagine that his head was the Earth, 
and his eyes the Observer's. The centre of his head 
would, for these Observers, be downwards, and, away 
from the centre, upwards. Thus he comprehended how 
the annual and diurnal motions go on together, the one 
not interfering with the other. 



EXERCISES. 

In determining the place in the Heavens of the Autumnal 
Equinoctial Point, we will again begin by looking to the Northern 
sky, and there we shall never fail to find our familiar friend, the 
Dipper, whose two foremost stars, the Pointers, will unerringly 
indicate the Polar Star, Cynosura, Taking, in our eye, Caph, 
Cynosura, and Megrez, and following on in that direction, about 



13. How did the father of our little traveller cause him to 
illustrate the union of the Earth's annual and diurnal mo- 
tions ? 



: T01CXAI roiNT. SI 

as far as f J there, the Autumnal Ooluro 

common intenectioi] both the Ecliptic and tho 

ction is the place of th< 

ben the ran i- in it ii 
In the days of Hipparchus, this Equinoctial 
n Libra, the Balance; bat now, by 
•i rem*, this BqaiBOCtia] Point 
the Virgin. ( tbeerre 
which form an im- 
•. and alao the beautiful 
:■ the Virgin*! Blade 
I I (lobe, she is n 
L Hipparchua, 1 28 J ears 1 i 
i the position o\ tins star. Lta change bn n 

Ddation of the certain knowl- 
edge - possess of the Procession of the Equi- 
now on the Elliptic 15° from the Ax- 
twm ate in the 1 1 1 
that we shall alwai k for it. 

•unj on the ( 

3 the 
arr.i!i_''i!i. !,♦ of the .-tar- on tin- pari of the Globe, In reference 

-t in 

the 

degree* «•; distance, and mark the direction of th*- following -tars 

• 

i 

in < »ri(»n <■», in 

are stars of tl ide ; and in no 

equal part and. 

■, study th<^ Southern Temp rate Z 

and learn * n<l H hat ; 

and • 

: land and of 1 ich. 



CHAPTER VIII. 

Time and Space. — Periodicity. — Secondaries of the Equator. 
— Terrestrial Globe made for the London Observer. — 
24 Semicircles measuring the Equator into 24 Equal Parts 
of 15° each. This Unit in Space equal to an Hour in 
Time. — Terrestrial Longitude ; how reckoned ; how cal- 
culated. — Circumpolar Stars. 

1. That Time and Space shall mutually measure each 
other, is an appointment of the wise Author of Nature. 
This appears by what some writers term Periodicity. That 
is, certain circuits are accomplished over determinate 
spaces, in the planetary system, in certain fixed and in- 
variable times. Of this the Earth, both in her annual 
and diurnal motions, the Moon, and the planets, all fur- 
nish examples. 

2. In our three systems, their Great Circles — viz., the 
Equator, the Ecliptic, and the Horizon — have each their 
Secondaries. The Secondaries of the Horizon we have 
already noticed under the head of Vertical Circles. We 
come now to speak of the Secondaries of the Equator — 
an important branch of Astronomical Geography. These 
Secondaries have a two-fold character, each circle referring 
both to Space , or Place, and to Time ; and it is in this 
double capacity that they are placed on the Terrestrial 
Globe, and shown in the accompanying diagram. 

3. This Globe is arranged for a located Observer, and 
for a specified day of the year, and hour of the day. The 
place of the First Observer is London. The Meridian 

Chapter VIII. — 1. How does it appear to be the design of the 
Author of nature that Space and Time shall mutually measure 
each other ? — 2. In the three systems before mentioned, what are 
the Great Circles ? What adjuncts to these are here mentioned ? 
What, as belonging to the Horizon ? What is said of the Secon- 
daries of the Equator as to their two-fold 'character ? (Draw 
and describe the diagram.) 



Hi: EQUATOR. 



83 




SJ» 



I OH tins ^1<» ] 

through that city. Thai rircamstsnce alone would aot, 

however, ti\ the Observer at London, since any <»tli«r 

Meridian might have been hie reai- 

it we know that it b from London or Greenwich 

that I in,. .n]y reckoned, iod thei 

the earth any other large city on this Meridian. 
According to the Globe, the 4 observer u at the moment of 
_r of the .' mt, a bioh h at m 

M.tnli. 

appean l»y the I I lea, tin* Ecliptic, 



For what if the ordinary Terrestrial Qldbt Arranged I W 

do we tuppote that 

doot Whit tj 

the Aatrooomical Tear begin t 



84 MERIDIANS— HOUR-CIRCLES. 

and the two Colures, which are brought down for this 
occasion, and marked on this Earth-Globe. Their posi- 
tion on the Globe suits this Meridian, and no other ; and 
it suits this Meridian at no other time. In four minutes, 
the Vernal Equinoctial Colure, here coinciding with the 
Meridian of London, will, by the Earth's diurnal motion 
towards the East, have apparently passed a degree to 
the West, — in an hour 15°. But the Vernal Colure is 
here coincident with the Observer's Meridian, and this 
common circle, composed of both, cuts both the Ecliptic 
and the Equator in the first degree of the sign Aries, at 
the Vernal Equinoctial Point. This coincidence happens 
to the London Observer only on the first day of the 
Astronomical Year, which, although the civil day com- 
mences at midnight, begins at xn at noon, and the 
Time-Circle around the Pole shows that this is now the 
hour of the Observer, for whom, at this special moment 
of the year and day, this Globe is expressly made.* 

5. The twelve Secondary Circles of the Equator, as re- 
lating to Space, are called Meridians or Lines of Longi- 
tude ; as relating to Time, Horary or Hour Circles. On 
the Equator (or equal divider of Space) they are marked 
with figures for the Longitude, or measurement of place 
and distance ; but on the Time-Circle, near the Pole, by 
Roman letters, indicating the 24 hours of the day. Both 
as Meridians and Hour Circles, it is more convenient to 
consider each Secondary as divided into two Semicircles 
at the Poles. When one Semicircle is above, and the 

* This Globe could not be made in this respect to suit all times 
and all Observers, but must, if these three Celestial Circles are 
placed on it at all, have a located Observer and a specified time. 
But great is the perplexity to teachers and scholars which they 
have caused. 

4. How does it appear that our London Observer must be at 
the beginning of his Astronomical Year ? At what hour com- 
mences the day as known in law, or the civil day ? — 5. How are 
the twelve Secondary Circles of the Equator named, as relating 
to Space ? how as relating to Time ? How are they distinguished 
in their two-fold capacity by the numbering on the Globe and in 
the diagram ? How is it most convenient to divide them at th© 
Poles ? 



85 

•n. the npper is oaUed die Superior 
and tin* lower lian. 

grand inYariable Uhh or Tim ii oin Rota* 

[fare ii no reason to 

1 by the Earth in making 

a di« by the retain to tome 

M. ridian, oould be determined by the 

r, thai there would, in a thousand y 

thousandth part of a aeoond 
In the obeen ao( the slightest devia- 

ity baa been discovered This 

Day. El into 8 i equal parte, 

e been arbitrary, y«t it is 

ma<i r " doll aii<l judgment, and it has 

intiquity. 

i of the Earth around 
its axia, every inied ar«>un<l 

• tho K.|i; 
account of the 
-. until at 1 • • 1 1 l: 1 1 i 
Hut 

io to 
each 
Ue passed over, in i 

8. . uniting at the 

twenty-four equal 
bleb 'is \:,\ The 
ie, paaaee in one 
hour over 16° i bow h 

Earth' i .'i'-n. the 

< ' -■ r\. r ; • ■■ - -■;. r l.~>. h.- will | » .- * — ^ owr <»n<* <h'gn.*e <>f 
8par . :ii". 

■ 
I 

•oticedf What U the name in all 

■mall I — 8 By what Baa, Kfl 

MsapparasA dally eoon*,pat»<- < v. r i:. manhaorl AaAbow 

■MBj degree io a miuut. nnl mh 

8 



86 ONE HOUR 15 DEGREES. 

9. To say that the Sun, in his apparent course, has 
moved over 15° of Longitude, is to say that he has been 
moving one hour in Time. To say that he has been 
moving two hours, is to say that he has moved over twice 
15, or 30° of Longitude. Indeed, it is not uncommon 
to use the one expression for the other. Thus, instead of 
saying that St. Petersburg is 30° E. Longitude from 
London, it might be said St. Petersburg is two hours east 
from London. 

10. As the Earth's rotatory motion is from West to 
East, so must the hours be marked on the Time-Circle. 
Observe this on the Globe. Our Observer at London has 
xn on his Meridian. Those whose Meridian has already 
passed from his Meridian 15°, have now i o'clock, p. m. ? 
while those who have gone on till their Meridian is 30° 
East from London, have at this moment their time at n 
o'clock ; those whose Meridian is 90° East, have vi ; and 
those who have gone half round the circle (180°), have 
midnight. But to those whose Meridian is in the rear of 
that of London, if 15°, then an hour must elapse before 
it is noon with them ; if 30°, then two hours — that is, it 
is with them x o'clock, a. m. Philadelphia is *75° (which 
is five hours) West of London ; wherefore it must be five 
hours before the Meridian of Philadelphia will have so 
revolved as to be where that of London now is, and it is 
there vn, a. m. Thus, universally, places East have earlier 
hours, and those West, later hours, than the located Ob- 
server, wherever he may be, whether at London or any 
other place. 

11. Turning your mind from the Globe, consider a real 
Observer at London, having over his head at noon the 
Vernal Colure, and inquire what will be his position as the 
Earth revolves on its axis. His Meridian, as we have 
said, will have gone 15° to the East of the Vernal Colure, 

9. What remarks are here made concerning the language of 
Time and Space ? — 10. How does your author here explain the 
hours marked on the Time-Circle of the Terrestrial Globe ? With 
whom will it be x o'clock, a. m., when it is noon at London ? With 
whom will it be vn o'clock, a. m. ? With whom will it be i o'clock, 

A. M. ? 



- 1 UKOU 87 

as li d has tamed in how away from, 

:i|»proaehe«l an hour nearer to, 
I with him it Will thm be i o'clock, P, m. As 

de from, and his Weal to ap- 

Bon, when BIX hours hav.» paOBCd an<l 

90° gone over, his Meridian will then coincide with the. 

at midDight it will be in the Autumnal 

Vernal will then be in the Meridian <>f 

tod in the morning, at vi o'clook, his 

Meridian >\ i • with the Winter Colore. 

me, will this * >h>erver's Meridian again 
be in tl. N-t precisely; it will have 

beyond, for the Earth 
has 1 from ^ ial daring ■ day, over 

h an •!--'. by which the Son in his 
trward thai bj 
r making a complete 
boal four mini 
<* ill be in the Meridian of 
• will tin. 

. tmine t 1 . and lie 

will fin- i marked 1 

wari ., following xn. What 

the London 
Ob*- ■ i hia h<»ur xii ; hut let 

Om that | 

. and LIS for an hoar, 
r under th<- Vernal ( blare, and 

will. . with it- 6X- 

:!;• If iv< o& . . The four 
riding tl 

- of 90° and u boon each. 

11. Whaiwfll un Observer at Loud 

i !.• tat t 1 

ridum ftw. it aro Uio 

foar principal Meridian* and i 



88 THE CHBONOMETEK. 

14. Terrestrial Longitude is reckoned East and West, 
180° each way from the First Meridian, until the two 
calculations, each amounting to 180°, meet at the oppo- 
site half of that circle. But here arises a confusion which 
sometimes obliges Geographers to reckon on beyond the 
180°. For example, the Longitude of the Eastern Con- 
tinent from Greenwich must be stated as extending from 
11° West to 190° East. For if we say that it ex- 
tends from 17° to 170° West Longitude, we then de- 
scribe just that portion of the Earth where the Eastern 
Continent is not. It is, therefore, maintained by some, 
that Terrestrial Longitude should, like Celestial, be reck- 
oned from the fixed Meridian East, quite round the 
whole 360° of the circle. 

15. When, by the united labors of Astronomers and 
Geographers, the invariable identity of 15° Space in Lon- 
gitude, and one hour of the day in Time, was ascertained, 
then the key was discovered by which unknown Longi- 
tudes could be found. Suppose a navigator, sailing on 
the Atlantic from London, wishes to find how many de- 
grees he has proceeded West from the Meridian of 
that place. He ascertains by the Sun that it is noon. 
His chronometer — for that is the name given to the care- 
fully-adjusted time-keeper made for navigators. — shows 
that it is two o'clock at London. Then he knows that he 
is in Longitude West 30° from London. 

16. But suppose some accident should damage his 
chronometer, so that he loses the London time ; or sup- 
pose he is on a very long voyage, and in a matter so im- 
portant as, learning his exact position, he is afraid to 
trust it, since man's work cannot be, like that of the Al- 
mighty, unerringly perfect. He wants, then, to find 
means of reference to the celestial bodies, by which he 
can gain the true London time. Various methods have 

14. How is Terrestrial Longitude reckoned ? What difficulty 
occurs from this mode of reckoning ? — 15. What is the key to 
finding unknown Longitudes ? Suppose a navigator sailing West 
from London wishes to find how many degrees he has proceeded ? 
— 16. If on a long voyage, what fears might he reasonably en- 
tertain ? 



Til MERIPLS 

Ppearam • been, of 

aa little as H 

that those distant moons would 

ally useful in 

•.'. ay, At what moment an eclipse of a satellite will 

and in London, ■ nautical al- 
io will show. Our i - for it with 

iiis cfalO- 

lon time. When he oom] 
d time, and Bnda their difference, he 
knows his Loi 

17. In regai I I i T er re stri al Longitude, there is no 
natural d .in: nor have the learned 

done die world the ier- 

to ajrree i * nations the He- 

: ital lias been made by 

Altrc»nnmei> the lir>t Meridian, <>r that of the First Ob- 

ude a certain 
of the ( i 
aged by thai posi- 

brs, th»* lii>t Ob- 
server is, how- posed to be located at London, or 

fitted 

up with telescopes, and all other necessary instruments 

The 

Meri London is sometimes called the u o'clock 

1£. - R ithout any «hii- 

until th- f the ^ rrer is i 

ieh any < »h-erv.-r -.-. -s i«\ ■ 

without ever 
[uala tie- Latitude 
ae Observer, those star* which 1 Dumber 

'. ill, in tie hr lower cul- 
mination, touch the Obsc-r rthern Borii 



IS. By what means might I 
What it Mid . : 

of the phrase, tara arc designated 

by Uut exprca- 

8* 



90 

those which are nearer will describe round the Pole, Circles 
of Perpetual Apparition ; and the stars which describe 
these circles are to that Observer, Circumpolar Stars, 

Heavenly bodies are at their highest, or culmina- 
ting point, when they come to the Meridian. The Cir- 
cumpolar Stars come twice to the Meridian in each 
revolution, and are said to have an Upper and a Lower 
Culmination, Those stars around the depressed Pole, 
which never rise, are said to describe Circles of Perpetual 
Occultation, The Polar Star itself has a revolution 
round the exact place of the Pole, from which it is dis- 
tant about a degree and a half. But this distance is so 
small, that for ordinary purposes it is considered as sta- 
tionary, and marking the place of the North Pole in the 
Heavens. 

19. The Analemma on the Terrestrial Globe is a dia- 
gram placed in some vacant spot of its surface, extend- 
ing through the Torrid Zone, and divided into months 
and days, corresponding to the Sun's Declination, or 
distance in the Ecliptic, from the Equinoctial, which for 
every day in the year may there be found. The month 
and day of the month being given — the Declination, at 
the time may be found ; or the Declination North or 
South being given, the time when the Sun is in that 
Declination can be ascertained, as well as the sign and 
degree of the Ecliptic. 



EXERCISES. 

Many problems of great interest, which may be worked out 
by the Globes, require us to know the Sun's place in the Ecliptic 
at a certain time. Find by the Analemma where he is at the 
day in which you now are. This will show his Declination, and 
by tracing at the same distance from the Equator round the 
Globe, you can see over whose heads he is to-day vertical. 

If we were perfectly possessed of the Uranography of the 
Circumpolar Stars, we could make them (having the knowledge 

18. "What is said of Culminating Points? What are Circles of 
Perpetual Apparition? of Perpetual Occultation? — 19. What is 
said of the Polar Star ? What is the Analemma and its use ? 



A CLOCK OF 8TAH5 PI 

of tr resent pla n kind of doc 

1 terms, toe timr t»t" night, If the 

\. and wo MS M' : jrc at 
limn, we know it i< Midnight. It' 
• aching the Upp.T Culminating Point, 

Learn from I lbs principal OoBsteDsl 

• th<> Oircilliipolsf Stars ; an«l 

learn rrinar OoUra and 

• m the Vernal 

the Autumnal Octal* — i. ft, from 

N itomosJ Colore to the Wmter 

md 4. Iliose from the Winter 

Point from which the calculation 

I 

On - • Dtionto the two Frigid 

en Ihe Arctir Cursls 

and ■ • ■ lying betwcN a the nntnrtie 

i tin. 1 bet 
tbem at to the land cont . 

hag in dT. T*it. 18°, He I 

with him 

of a r utn- 

Isrenen, or I from London And .<ii.es the Earth turns 
Eaat» ♦'» o'clock m the morning towards 

noon. Hw Longituds ia, therefore, 90° West of London) and Mi 

' i nl f of >I< xico, with the 
noddy cut -" around 



CHAPTER IX. 

Terrestrial Almacantar Circles, — how used to divide the 
Earth into Six Belts; being an easy Method of obtain- 
ing a General Knowledge of the Distances of all Places 
on the Earth's Surface from our own Position. 

1. Having, in the exercises on the Terrestrial Globe, 
endeavored, in the first place, to lead our students to con- 
nect all places on the Earth's surface with the Permanent 
Positions, the Equator, its parallels, and the Zones which 
they include, we would now aid thern in making a second 
and subsequent arrangement in reference to that useful 
law of our nature, by which every person must not only 
regard his own position as immediately under the crest of 
the sky, but also as constituting the very centre of the 
world in which his field of activity lies. By this law, 
man, in order to make his knowledge of Astronomical 
Geography useful, must connect it with himself. It is 
well to know the distance from each other of cities and 
countries ; but their distance from himself is a great item 
of general information, indispensable to the man of science 
or of business. 

2. We offer here an easy method of obtaining a gen- 
eral view of all terrestrial distances, by dividing the Earth's 
semi -circumference from our own position in the Upper 
Vertex to the Lower Vertex, or the position of our An- 
tipodes into six Belts, or Zones, by five Almacantar 
Circles, of which the Rational Horizon is the third or 
central. (See Fig. 2.) 

3. Reckoning the mean circumference of the Earth at 

Chapter IX.— 1. "What principles ©f our nature are here re- 
ferred to as important to be regarded in education? — 2. What 
method of obtaining a general view of all terrestrial distances 
from our own position is here developed I 



IMPORTW i i u>r;r 93 

.* the half of that O M T CtH P fci eDee, as □ 

•in of Terrestrial 

bd their Polei in the Upper and Lower 

I miles. This half will be equally 
or 11 r which these Vertieab 

secondaries, an 1 from either the Upper ot Lowei Vertex 
will be one quarter of the Earth's dr- 

• subdivided 
i, cutting the ( . )(,: between the 

the Upper and Lower Vertices: into three 
aeh. If SO be multiplied bj 
miles in ■ degree, the product will 
r is will be obtained 
. 
six equal 

• 2,07Q miles* 

be com] I by l efete n ce to 

• • world in whieh we have sup- 

posed ourselves lo ■ V rk. The 

V« -rk SS 

• it, and two 

ad the Boriaoo. 

of die ( ' 

. tin- Indian Ocean, South- 

• TUl k only 16 mflftl less than the estimate marie on >ir Joha 

ri mean diara 

Most author-, bom 
Earth's axis as 8,000 mi miles 

in a degree as 69 J, which is too d on the loppoaitton 

that the Eartl, which it i- ii"t. 

HL = 

half of whieh, of shs m 



serrer or Axu» 

equal parts, by points, and draw tin 

angles to the axis. These will dil 

aumher indicr si ■ tlio 

width ei sash Zonal 



to mi:.' era. 95 

West of v Hand, where ia no land, a ship ia there 

place*!, and id ur Antipodes. Prom this 

irtli, small as it is, \\«> can, by means 
-remembered numbers, de- 

tlif di>tamvs of all places OD the 

A idmplo ]>i<v of nuvh- 

containing the two Alma- 

1 !• misphere, as described : or 

- of 30° and G0° radius might be 

olving tlif quadrant of 

altit Barest our own position we term the 

the Borixon, third ; the nexl 
• the Antipodes, fifth : and 
by the Lower Vertex, or pi 

I from the Upper 
m on the Firs! are bom the ( i 

thai dis- 

n the Third. < r ! I- ri/.m. 

Urn- is a quar- 

4 and it is exactly the 

nml will produce. 

6. Should * and, for the pur- 

pose n, put the Lo tei in the place of 

the 1 ild enable u> to meas- 

irth, Th< next 

. macantar, end its distance 

I by sdding the increment 

i bird, or Soriaon, and it is 

pposite 
Grand by adding 

• t.. t!i.- ii. \t pn-r.-dimr, 

• At the sugsetti 
preparing the AlmaesBtai OMet lot sk globe* 

4. FrcifD whxi' 
do we find at - 
rr e ae e a» we : 

. ;h !},.• | i All- 

i f What can you «ay of that point of i . 



96 DISTANCES FROM THE OBSERVER. 

and it is from our position 10,350 miles. Adding the 
same, we find the distance of the Sixth and last Posi- 
tion to be half the circumference, 12,420 miles. This is 
the completion of our plan, and it brings us to the place 
of our Antipodes — if, by the presence of a vessel at sea, 
we happen to have any. This is the only place on the 
Earth's surface, and it is but a point, which is thus remote 
from ourselves. Whatever people may be there, they 
have their feet opposite to ours, and that is the reason of 
their appellation — Antipodes.* They are on the opposite 
talf of our Meridian, as many degrees from the South 
Pole as we are from the North. 

8. Intermediate, then, between the Upper and Lower Ver- 
tex, we have five Almacantar Circles, of which the Ho- 
rizon is one, dividing the circumference of the Earth into 
six equal distances from the Observer, so arranged as to 
be easily measured. For if we choose to throw away 
smaller numbers, and consider the Earth's circumference 
as 24,000 miles, then the First Distance will be 2000, 
and the increment of increase 2000 ; so that the 

First Distance will be 2,000 miles. 

Second " " 4,000 " 

Third « " 6,000 " 

Fourth « " 8,000 " 

Fifth " " 10,000 " 

Sixth " " 12,000 " 

9. This is the more easily recollected, as the number of 
the thousands is the double of the number of the Dis- 
tances. The thousands go from two to twelve, and the 
Distances from one to six. If greater accuracy is re- 
quired, we have but to recollect that 70 is to be added to 
the First Distance, 2 x 70 to the Second, 3 x 70 to the 
Third, 4 x 70 to the Fourth, 5 X 70 to the Fifth, 6 x 70 
to the Sixth. 

* Anti-podes— opposite feet, from podes, the Greek word for 
feet, and and, opposite. 

&. Recapitulate so as to be perfect in your recollection. — 9. 
How can we show that these numbers are very easy to be rec- 
ollected ? 



■DOB DfOWH BY l.in: 07 

10. The Zo: ppet and Lowei V. rticee 

msmai'. then. The two which are 

• i the Horuon we much the largest o( the i 

remaining intermediate in sLu as in 

these sur&oea into square miles, t 1 

Z<me$ — t! rounding (he tipper and 

as, and tl n1 — each contains 

i dies; the Si oond and Fifth, or inter- 

i.ites, each oontaii I T l ; and the Third wu*\ 

• •so a«lj:uvnt to the Horizon, and the laq 

. »;<,:•; 1. T.. nvapitulate: 

I square mile*. 
.. 80,994171 
urtb, 

one- 

i. Mul- 

obtain as a product the 

mfrce o( the 

.."iOO. 
Jler numbers, and robti 

Snd that the ram 

• be lower with only the 

s w Inch multiplied by 

umber (nearly two 

hundred milK . thai it may be thrown 

I — 
le of a Bph e f O - < 
tains ha/ <<t* that 3 

* ] 
six Belu was besor John A. Niehols, o 

Free Academy 
latino, h»- Menu to Le as 

' B6W many 
tqaare mile* havp the two larfre- 1 

■MDeetl the two Intermediate 1 How man y has the Berth I 
What rule u here menlionel, and how U it obtain- 





98 



beyer's method. 



EXERCISES. 

When, in looking upon the starry Heavens, we reflect that 
Astronomers know and name every star which we can distin- 
guish by the eye, and many which we cannot, it gives us a sub- 
lime idea of the powers of man, as well as of the works of God, 
When the stars were arranged into constellations, a work was 
done for Uranography, as has been already noticed, similar to 
what was done for Geography when the land was divided and 
the countries received names ; and when the principal stars re- 
ceived names, it was as when great cities were thus designated. 
But there still remained a vast number of stars of which there 
was no distinctive appellation, much to the annoyance of Astron- 
omers. 

M. Beyer, a German, of Suabia, found a method of remedying 
this difficulty, very simple to those who know the letters of the 
Greek alphabet, which are — 







Name. 


Sound. 






Name. 1 


3ound 


A 


a 


Alpha 


a 


N 


y 


Nu 


n 


B 


06 


Beta 


b 


E 


i 


Xi 


X 


r 


7 


Gamma 


I 


O 


o 


Omicron 


o short 


A 


6 


Delta 


n 


It 


Pi 


P 


E 


e 


Epsilon 


e short 


p 


9 9 


Rho 


r 


z 


^ 


Zeta 


z 


2 


<T S 


Sigma 


s 


H 


V 


Eta 


e long 


T 


r 


Tau 


t 


e 


30 


Theta 


th 


Y 


V 


Upsilon 


u 


i 


i 


Iota 


i 


$ 


<P 


Phi 


ph 


K 


K 


Kappa 


k 


X 


X 


Chi 


eh 


A 


A 


Lambda 


1 


¥ 


* 


Psi 


ps 


M 


V- 


Mu 


m 


a 


M 


Omega 


o long 



In every constellation stars of the first magnitude are desig- 
nated by a, those of the second by /?, those of the third by y, and 
so on. When the stars in any constellation are so numerous as 
to exhaust the letters of the Greek alphabet, Roman letters are 
then employed. 

If the two Almacantars mentioned be placed upon the Upper 
Hemisphere of the Celestial Globe, the Observer's Zenith being 
placed in its true position (the time of the year and the day 
given), it will be a beautiful problem to find the principal 
stars upon them — especially those on the Upper Almacantar, 
they being at 30° distance from our Zenith at the moment 
specified. 

What is the Declination and Right Ascension of the star of 
the first magnitude Antares, in the Scorpion's Heart ? of Fomal- 
haut, in the mouth of the Southern Fish ? of Altair, in Aquila, 
the Eagle? Declination and Right Ascension, it will be recol- 
lected describe these stars in respect to their nearness or dis- 



WHY Tl 

tance from the Equinoctial and its principal secondary, the Ver- 
nal O 

. »:il Globe. to the preceding chap- 

• arn what -. seas, ielanda, and large cities lie on the 

own poai- 

ind with hk i.i 

begin at : trace towards i then South 

scribe in that order what 

find on this circle, ai iBOe from your own poei- 

Learn in the same manner all the [ivinOM oi' land and 

- which ti. tar Circle 

pasF< thai the distance of these various 

■ 

: to the a mb ition and intelli- 
formataoflL The am- 
is and a! I will include in th< ir r - not 
only all we have n. 
mountain-ranges an I and tell wh I vers 

In studying by these five Almacantar*, remember that the 
nearer are the placea to your mvh ]...Mti«'n. the mote minute 
should be jour knowledge of them. 



CHAPTEB X. 

muaj r>r the Seasons, and the Causes, 

1. band the 

cans* rfl is tki 

nual m* r ■ '. with to Ax - 

• 
The incl: - of our | 

aa we have seen, 66 J, — the com] 

the 

tame wl ■ with the | 

plar 

the Axii i 



100 ON THE TERRESTRIAL GLOBE. 

of the Equator. Our subject thus leads us to begin the 
consideration of the intersections of the Spherical Sys- 
tems, which will be more fully developed hereafter. We 
shall see, that upon the angle made by the axes of the 
systems, depends not only the changes of the seasons and 
the alternations of heat and cold, but the share which 
any observer or individual on the Earth will receive of 
each. 

2. A part of our object is to understand the Globes. 
The Ecliptic and the two Colures — three circles which 
belong solely to the Celestial Sphere — are marked on the 
Terrestrial Globe, and the instructor can find on it nothing 
which explains how or why. This deficiency we endeavor 
to make up, according to the best of our power. As 
the three systems are spherical — that is, made up of 
spheres — the Earth's surface is a sphere concentric to the 
others, whether we conceive them to be little or much larger ; 
and every axis of each must pass through the Earth's 
centre and also the plane of every great circle, which 
must divide the Earth into two equal parts.* The Ecliptic 
is a great circle, and the Colures are great circles, and we 
may conceive that their planes, dividing the Earth, leave 
their traces on the Earth's surface, where they intersect it 
in passing forth from the common centre to extend out 
every way to the Heavens : and so the maker or designer 
of the Artificial Terrestrial Globe has imagined ; and he 
has thus marked these intersections on the Globe, calling 
them, as you perceive, the Ecliptic, the Solstitial Colure, 
and the Equinoctial Colure. 

* See Fig. 1. 

1. To what does our subject lead us? What shall we be 
enabled to see ? — 2. What three great circles of the Celestial 
Sphere are marked on the Terrestrial Globes? Why do we 
call our three systems spherical ? When a smaller Sphere has 
larger ones inclosing it, all having a common centre, what do 
we call them ? Where must every Axis of each pass ? Where 
must the plane of every great circle belonging to any of the 
concentric spheres pass ? and how divide the Earth ? Where 
may we imagine these planes to make circles ? How, then, are 
we to suppose that the designer of the artificial Terrestrial 
Globe placed those three great circles upon it? 



ram I L01 

3. But even tl. ilv 

of place . * ii « L 
of t; se the time to 

be t ring of the astronomical 

tad the place 
re on th< q. At this time 

ind of the 

l tie 1 « rrestrial Sphere, where they 

e as they appear (Hi the Terrestrial 

t:<k«> the Bame time and a different 

: l»«- wrong. lake Now fork, for 

ronomieal year, which 

March (the day of 

en the line of the Vernal 

fork instead 

of 1. Solsl must 

be e Or, 2d, lei it be London at 

the I 

lure inn toad ■ 

_!it of aba lobe 

t: • — L -r. .• ■ r • • -. }•••!•. i!Lrii._r >>>\v)y t<> tlu* ( '< li->ti;il 

M Mian, at. 
observer's hea 

4. 

s 

this 
parallel I 

m of 
and the Ecliptic, 
oitely, but a! 
keeping the sam* i with reaped to th- 

is a 



S. How fkr i 
if presupposed I 

I the wime place 
ii your antl 
Colore* on thr atep 

first to be taken in 'our illuatra* I Seasons f 



102 



THE FOUR SEASONS. 



plane parallel to our assumed imaginary plane of the 
Earth's Orbit, which, of course, always passes through the 
Earth's centre. . . . We will further prepare for our ex- 
periment by closing the window-shutters and lighting 
this small lamp. We have prepared it for the occasion, 
and it is of such a height that its centre is in the same 
plane as the centres of the Earth and of the wooden 
Horizon, which are both in the plane of the Earth's Or- 
bit. We are not now to be observers in a geocentric 
position — that is, on the Earth's surface, attending to 
mere appearances — but we must imagine ourselves to 
occupy a heliocentric position ; that is, to be looking out 
from the Sun, and understanding things as they are. But 
whenever the apparent motion of the Sun is described, 
we must come back to our geocentric position. 

Fig. 13. 
SUMMER 




5. Now, we will move the Globe around the lamp in a 
manner to explain how the annual revolution of the Earth, 
with this inclination of the Axis, causes the succession of 
the four seasons. We must fancy this wooden plane to 
be nothing but an imaginary one, and of course obstruct- 

4. What farther preparations are indicated for the experi- 
ment to be made ? What is a geocentric position ? — heliocentric * 



srK *d summi 103 

og do shadow; wad we must boar 
in mind that Kgfal falling on a Globe from one direction, 
rjust half its surface, and no more, 

6. 6 Globe in this first of its four poiri- 

that it represents the Earth at the 

fj Equinox, when the Sun enters the 

j, This, we must recollect, is the rigm, and 

tellation Aries; since, on account of the Pte- 

. the Sun is now in the const rl- 

5un at the moment, as the lamp on 
our G tally to both Poles. The days and 

[Ual all over the Earth, and with us in the 
Spring, 

a quarter of the Earth's 
! i is the line made by the centre of 

a> \N<- ar«»un<l our poor substitute for 

•n in which the Earth 

•lution K bj definition in 

from 

on apparently 

psAs Lries through Taurds and Gemini to 

. Nvliidi it - 1 of 

Jun» through which the Sun ap] 

ea, Aries, and Taurus, 

bas at this time his northern 

dec!: Equinoctial, and after 

1 for a few days in this S r Sol- 

again in his apparent course to- 

th. It i hat the ancients gave 

UatlOn which the Sun 

aras in ; age by the Pi of the EEqui- 

ioxes; because the crab moves both backwards and for- 



5. How I the Qlobs round the lamp to be 

ombV to be placed 1 What arc we 

ightatth -7. Describe U ippa* 

: oH'it from U 
■ 

the name 
f the cootie! latioo Can 



104 ATJTUMH AND WINTEB. 

wards; and the Sun from this point goes back to the 
Equator. 

8. But, as we move our Globe, we must keep in mind 
our main object— which is, to observe how the rays of 
light and heat affect it, as it moves. In going from the 
Spring to the Summer position, keeping the axis always 
in the same direction, the North Pole becomes wholly 
enlightened, and the South Pole sinks into shade ; and 
when we have reached the Solstitial Point, this northern 
polar light will extend beyond the Pole 23^- degrees, 
and the southern polar darkness will do the same. But 
they have now both reached their extreme limit. 

9. We will again remove our Globe in its orbit an- 
other quarter, from the Summer to the Autumnal po- 
sition. During the removal, the Sun in the Ecliptic will 
appear to move through the signs Cancer, Leo, and Vir- 
go, and through the constellations Gemini, Cancer, and 
Leo to Virgo. He enters the sign Libra on the 23d of 
September, The constellation Libra, the Balance, from 
which this sign was originally named, is supposed to have 
received its appellation in early ages, because ^the Sun, 
when in this constellation, gives an equal or balanced 
light and heat to all parts of the world. This is the 
Autumnal Equinox, when again the Sun has no declina- 
tion, but is in the Equator of the Heavens, and, as our 
apparatus shows us, his light shines equally to both 
Poles. 

10. We will now carry our Globe through the third 
quarter of its circuit, from its Autumnal to its Winter 
position ; the Sun meanwhile passing through the signs 
Virgo, Libra, and Scorpio, to the first degree of Capricor- 
nus, when he is in our Winter Solstice, having 23\ de- 

8. What is the manner in which the rays of light and heat 
affect the Earth as it moves from the Spring to the Summer po- 
sition ? — 9. While the Earth moves from the Summer to the 
Autumnal position, how will the Sun appear to move both with 
respect to the signs and the constellations ? When does the Sun 
enter the sign Libra ? What is said of this name ? What is 
this time ? — 10. While the Earth moves from the Autumual to 
the Winter position, where does the Sun appear in respect to 
the signs and constellations \ 



RKLLATIOm. 105 

g re cs o( v don. During this quarter ot 

3ie Earth's motion, the light has been receding from the 

t in darkness ; and, 01 eoura 

on half the Globe, hia rays hare in 

same degree - d the Earth beyond the South 

g, which is, of course, 

rn Kght and northern dark 

li. Son, when he mores from thn I s "/- 

m in his apparent course to the 

(oinoctial, when again his rays will 

uatoT of the Earth. We will now 

:r.'»iLrli this last of the four quartern of 

from \\ Spring. The signs 

S .!i will more are Caprioornus, A.jua- 

i ling one behind 

Lquarius, leaving him 

str<:»nomical year, with the 

degree o; . Aries, and in the Krai of the i 

; hn Her- 
oical subdivisions 
with the actual Equinox, 
and are i \\ ith the conateDationf 

!. The constellations 

arrangi I on the Eclip- 

tre all a : pation of their 

marked/ 1 To tiroid this 
• rdinary reckoning 
pees, from <> to 860°, will, he 
I the oames, Aries, V 

■ called. 

* In advance, aa respect- oxea. 

11. » 
nal ! 

• 

this awkward discrepancy between the aigua an d 
1 1 



106 "beauty and beneficence." 

present, however, when it is said the Sun is in a certain 
degree of Aries, Libra, &c, we are to understand the 
signs of that name, and not the constellations. 

13. The contemplation of the Seasons in all their 
variety of usefulness and beauty, lifts up our hearts in 
adoration of the Wisdom, the Power, and the Goodness 
which thus adapts all parts of nature to each other and 
to man ; and we recognize in them the hand of a Bene- 
ficent Father who loves to please, as- -well as to preserve 
his children. Well does Thomson, the harmonious poet 
of the u Seasons," exclaim : 

" Mysterious round ! what skill, what force divine, 
Deep felt in these appear ! a simple train, 
Yet so delightful mix'd, with such kind art, 
Such beauty and beneficence combined ; 
Shade, unperceived, so softening into shade, 
And all so forming an harmonious whole ; 
That as they still succeed they ravish still. 
But wandering oft, with brute unconscious gaze, 
Man marks not Thee, marks not the mighty hand, 
That ever busy, wheels the silent sphere ; 
Works in the secret deep ; shoots, steaming, thence 
The fair profusion that o'er spreads the Spring ; 
Flings from the sun direct the flaming day ; 
Feeds every creature ; hurls the tempest forth ; 
And as on earth this grateful change revolves, 
With transport touches all the springs of life." 



EXERCISES. 

In all our attempts to give instruction on great astronomical 
subjects, we are liable, by our illustrations, while we afford 
light and truth, to introduce some error and confusion along with 
it. In moving our terrestrial globe around our mock-sun, we 
show how the revolving motion with the inclined axis produces 
the change of the seasons. But the student will find his mind 
confused on account of the direction of the plane of the Ecliptic 
and Earth's orbit, and it will be but by slow degrees that he will 
be able to acquire clear ideas on this complicated subject. 

The Ecliptic is determinate in space, else the Sun would not, 
as the Earth, year after year, goes round him, be seen always 
passing in his apparent Ecliptic-path through the same groups of 
stars. But to Observers on every side of the Globe, each sup- 
posing that over his own head is up, aud the contrary down, the 



TFTF. BO U PT IC TRACED. 107 

ne to have a different direction. Thn 
i$ al*o, in degree, the CAM With the ByUPOCtUI, out its ohajo 
are much more easily on itnce to BTery obserrer it al- 

ways crosses th in the points. ea>t and west, while the 

etually during the '24 hours, by the Earth's 

m, and endeavor to cone.-ive 
the Ecliptia Suppose we are look- 
ing upon the sky at midnight on the 80th of March, The Bon is 

a it is midnight) he is in the Me- 

Nadir. In our Meridian is, at thifl moment, the 

WenMOR The Autumnal 

with one Meridian. The Winter 

- Right Ascension -7<> D . 

is iu the rear, haying 90° of 

n, i- the Kelipl i I ad wh. re 

liptie which is u»>w iu our view ? 

Elevate, as bef I tie- Oelestial (Jlobe a 

niun'i Mule, and bring the Au- 

itndj the 
will inform n - 
on t." Pole of the Earth. 

sell tie- 

stars, it will be a k in of the 

tn it.-, 

e and on the Winter 

that < olore, be S 

Sout b rn declination, «-r 

it-* greatest possible distai o- from our Z.idth. Thru of oonse- 

. Point will be 28] ; North of 

lure. 

the two F.qui- 
..il and th« two S intsj there will now be — Let, 

i idian, where it crosses the 
• low your Hoi 
south of esst ; ini in the opposite Heavens 

b mm • he Berth 

n of thai 
half • ps acroei 

i ct by th- i 

1- will bo a to tin l an 

eraeetion* I a< i- the from the 

Isfiptic i- situated .-it the tame time and place. 

Earth's surface by Almacant.. JmsY 



108 INTERSECTIONS OF SYSTEMS. 

cantar (the Rational Horkon), and as this is so much the largest 
Circle, it will be well to divide it by the points of Compass, as 
expressed by the Horkon "What seas and lands do you find on 
the Third Almacantar from your own position in its passage from 
north to east ? from east to south ? from south to west ? Bear 
it constantly in mind that all these places are distant from you 
6,210 miles. If you forget the odd numbers — in your recitation 
you may say about 6,000 miles, or more than 6,000 miles — but 
it will be easy to calculate them by merely remembering the 
number 10 to be added to the thousands, multiplied by the num- 
ber of the Almacantar Circle as reckoned from your position. 



CHAPTER XI. 

Permanent Positions arising from the Intersections of the 
Systems of the Earth and Heavens. — The Tropics and the 
Polar Circles. — Different Planets have their Axes at 
Different Degrees of Obliquity. — The Five Zones. 

1. The Tropics, the Polar Circles, and the Zones are 
Permanent Positions belonging to the System of the 
Earth. They are all parallels to the Equator ; but the 
Tropics and Polar Circles, which fix the location of the 
five Zones, are not, like ordinary parallels of latitude, to 
be drawn at pleasure anywhere between the Equator and 
the Poles. They have by nature determinate positions, 
and these are derived from Intersections between the 
System of the Earth and the System of the Heavens. 
These two Systems belonging to the Permanent Positions, 
their Intersections will also be the same. 

2. We must be careful to understand the Systems as 
they exist singly — each by itself; and their Intersections 
will then be less difficult. In any two Spherical Systems, 

Chapter XI. — 1. In what respects are the Tropics and Polar 
Circles like ordinary lines of latitude ? and in what respects are 
they different ? What are the places of these four circles de- 
rived from ? How may we know that they are Permanent Po- 
sitions ? — 2. Of what two Spherical Systems are we now to con- 
sider the Intersections ? 



IXTKRSI-a rioN 01 rDABtn. 109 

ns hai b&tm ihown, n< is the a)i>;!r uvnle ?>>/ the /afafU fr 

will be the tmgU% *f their gt 

■ rr!( s. 'I'll,' urn 

oi mentioned, an 

s, the Ecliptic 

.1. The aam< io be made 

— viz., those of celestial latitude and 

reg ird t-> the angles made by the 

Secondaries of the great dicks, the convexity of the 

a but one, will cause tin 1 

That one Secondary of each 

. is that which, in the System 

I msm through the first degree <>t* the 

1 that which, in the System <>t* 

-••- thr-»u;_rh the same Points, and IS called 

111- — two S»M7»n«larifS cut 

::<>n. 

which make an 
larjr .e angles ffrow less an 1 less, until, with the 

. 
--, ami ti. S inei.h — 

through the first 

< t* < ' u.. . r aip] * 'a].ri«-..rn, with thai of the Equinoctial 
pa*> 3 ts, and called the Sol- 

ami Libra int 
sect- 

whi 6 j with the firsl <.-t ( lan- 

cer ai rvening Secondari 

each S of tii" 1 [eavena, 

% Suppose the A 

•i, -what >•'• ! make I ; 

similar angles ' 

the two Systems n> two Sec 

•ect at the common angle d 

that W hat can you say 

of each System I 

: 



110 CARDINAL POINTS OF THE HEAVENS. 

Secondaries of Celestial Longitude, and in the System of 
the Earth, the Secondaries of Right Ascension, make 
angles which go from 0° at the Solstitial Colure to 23^° 
at the Equinoctial. So that at the Solstitial Colure, Celes- 
tial Longitude and Right Ascension coincide throughout 
the common circle, but they vary elsewhere, except at the 
angle of their Intersections. Let these Intersections be 
verified by tracing them on the Celestial Globe. 

4. An arc of the Solstitial Colure intercepted between 
the Ecliptic and the Equinoctial, is the greatest possible 
distance between them, and is the measure of the angle 
of their intersection. An arc of the same Colure and of 
the same extent, measures the distance of the two North 
Poles of each System ; and also the distance between their 
two South Poles. This arc is the measure of the angle 
made by the Intersection of the Axes. The two Equi- 
noctial and the two Solstitial Points are sometimes called 
the Four Cardinal Points of the Ecliptic ; the Vernal 
Point being the Zero (0°), or initial point of both Celes- 
tial Longitude and Right Ascension. As in time we go 
from Spring to Summer, so the Summer Solstitial Point, 
tracing in the Ecliptic from west to east, is 90° east from 
the Vernal Point. Autumn follows, and the Autumnal 
Point is 180° next west in the order of the signs; and 
the Winter Point has 270°, and these degrees are both of 
Celestial Longitude and Right Ascension. Then from 
Winter to Spring is 90° more, which will complete the 
360° of the Circle. 

5. In asserting that the Intersections of the Permanent 
Positions are Permanent, it is proper to mention that there 
is a slight change in them, going on constantly, though 



3. This subject being of importance, you may recapitulate the 
manner of intersection of the Secondaries of the System of the 
Earth with the System of the Heavens. — 4. What arc measures 
the angle of intersection of the Ecliptic and the Equinoctial — 
of the distance of the North Celestial Pole of the Earth and 
that of the Ecliptic? What are the Four Cardinal Points of 
the Ecliptic? What degrees both of Celestial Longitude and 
Right Ascension, and what seasons of the year, commence with 
each of these four Points ? 



- nagMouro. Ill 

is may hi stood in consider- 

: the R< d of the Equinoctial 

lost intricate 
calci; For all the important pur- 

poses of >graphy, however, these inter- 

lacing Pi niuntiiit Po- 
y will never, in any case, t'all under lliose 
h wo haw applied the term Movable — 
a the changeful place of the hu- 
man ' ing in either of these Systems is 

QS Of tli«' I 

two 1 'ermanent Systems will 
prodv 

6. Althougl 8ysi its funda- 

not always the first-found flo- 
»ume that tho 
time 
ire equal over the wh< 
was ' System. 

and Poles an 

and 

also. I treat 

My," 
apparently i ma through 

In lik-' manner, ^ hen the 
- an arraagi . into "no 

f the /bees, -3^°, 
is tl . thai Brat noticed will 

it the Int. • 

■ 

will bi f : 

; — »'.. \Y)j;it <lif- 
ferencc u here Dot 
rr.ier'J t limtn l of :i Spherical >\ -* • rn. nn< 1 what Kl Um fuixla- 

fnl f"*:n 1 tlasaspl of Mi.- K.irth'* System) The Great Circle <>f 

«tem being given, how ar 
do we presume to have been I 

tcm of the Hcayi n- ? What sag)* ^y*tcina of 

the Earth sod Heavens ii the leading angle f and why I 



112 THE TWO POLAR CIRCLES. 

necessarily be the angle 66^°, or the angle of the Axis 
with the common plane of the Earth's orbit and the 
Ecliptic, which is the complement of the first angle, 23^°. 
For it is the coincidence of the Earth! s orbit with the plane 
of the Ecliptic which constitutes the necessary connection 
between the two Systems. 

7. We will now consider how the Intersections of these 
two Systems give rise to the Polar Circles and the 
Tropics. If we suppose the Axis of the Ecliptic to be 
revolved from the centre at an angle of 23^° about the 
Axis of the Earth, it would mark upon the Earth's sur- 
face the Polar Circles. That around the North Pole is 
called the Arctic Circle, and that around the South Pole 
the Antarctic. The Sun, in his connection with the Celes- 
tial System, has his centre cut by the plane of the Eclip- 
tic, and his central vertical ray always passing towards the 
centre of the Earth, in the same plane. His extreme 
rays then falling on just half the Earth, will always ex- 
tend to the Poles of the Ecliptic, and no farther. 

8. Now, the Poles of the Ecliptic are in the Solstitial 
Colure, which crosses the Equinoctial Colure at right 
angles in the Earth's Celestial Poles ; while the Equinoc- 
tial Colure crosses the Equator at the Equinoctial Points. 
The Solstitial Colure, therefore, crosses the Ecliptic at the 
two opposite points where its distance from the Equator 
is the greatest, and where the Sun is at the time of the 
Solstices, and which therefore forms a limit to that por- 
tion of the Earth where the Sun's vertical rays fall. The 
tivo Tropics are drawn through these Solstitial Points, 
and made parallel to the Equator, of course at the dis- 

6. But what is naturally the first noticed ? What constitutes 
the necessary connection between the two Permanent Systems ? 
"What are the degrees of each of the angles mentioned, and what 
are their relations to each other ? — 7. How, from the Intersec- 
tions of the two Systems, are the Polar Circles produced ? What 
are they called ? From what circumstances concerning the Sun 
is it apparent that he is always shining just as far as to the Poles 
of the Ecliptic and no farther ? — 8. What is here said of the Sol- 
stitial Colure ? what of the Equinoctial ? Where, then, are the 
two Tropics drawn, and what is said of the names by which they 
are distinguished ? 



Tin; two raOPKB. 1 L8 

ft en they received their names, the 

< • the Northern Solstitial Point, 

an.i • t theS uthern, and from these eon 

- of Cancer and of 

,iiit v which the Axis of any planet 

tion with the plane of its Orbit, is, 

as we liv or chapter on the Seasons, of great 

sign; rth'a A\> is, as we have already 

hapter, oblique to the plane of its Orbit 

• Lris of the globe 

per]' [which, for this purpose, we 

will Soriaon to be), the Equator 

woull th* ith the plane of the Ecliptic. Hie 

revo. rth around the Sun would, in this 

: for tli* 4 Sun, Ifl 

• un«l a lamp, 

jiially upon the whole 

. an<l 

.rlv the i 

I • . : thai planet, 

.on account of tl rom the Sun, 

d ourselves, have not 

Y. t their planet, being 

so large, a great snrfa the Sun, like 

• ver- 
. 

i be coincident with, 
or \\- it would, «'»t the period of 

iu I. the 

l Bhining equally 
iding with those of the 

► oulc] 1 [ual. But •• 

m the Vernal to the north 
ason 
3 

9. Suppose |] 
pass the A !;me of its 



114 



DIVINE WISDOM. 



rays would fall direct upon the North Pole— the whole 
northern Hemisphere be enlightened, and the whole 
southern in darkness. This is an imaginary case. No 
known planet has its Axis parallel to its Orbit. It im- 
plies changes so great and rapid, that no animal or vege- 
table known to us could endure them. 

11. We recognize the goodness and wisdom of God in 
inclining the Axis of the Earth, so as to accommodate 
the creatures which he has made to inhabit it. Mars has 
his Axis inclined to the plane of his Orbit 30°, Saturn 
(distinguished for his bright rings) at an angle of 29°, 
and Uranus probably at the large angle of 46°. If these 
and other circumstances vary the climates of the different 
planets, the inexhaustible wisdom of the Almighty will 
doubtless have suited the planets to their inhabitants, or 
the inhabitants to their planets. 

12. Every place on the Earth's surface lying between 
the Tropics, has the Sun's direct rays shining upon it 
twice each year. At the Tropics he is vertical only once 
a year, — in the Northern, at the Summer Solstice, and in 

Fig. 14. 




the Southern, at the Winter Solstice. From the convex- 
ity of the Earth, the climate is hottest where the Sun's 
rays are direct."* This belt of the Earth's surface between 
the Tropics is called the Torrid Zone, and is 47° broad. 

Compare the number of rays falling near the Equa- 



* Let Fig. 14 be drawn large, 
tor and the Poles. 



10. Do we know of any planet in this case ? What conse- 
quences would follow ? — 1 1. What is the position of the Axis of 
Mars ? of Saturn ? of Uranus ? For what is Saturn distin- 
guished? Do we recognize wisdom and goodness in the arrange- 
ments by which the Almighty has prepared man for a planet 
whose Axis is inclined as ours is ? And suppose other planets 
do vary, what may we conclude concerning their inhabitants? — 
12. Where is the Torrid Zone, and what is its breadth? 



THE nOT US OOLD ZOXES. 115 

In v. ns, tlie Torrid Zona shows the for- 

the Sun'- rays, ,5 

BOflM and fruits together riot, 

if in gay confusion lie?.'' 

But man Ibf labor, and in this Zone, as be 

<>r clothing, and his food grows spon- 
tane- but too men an indolent, nnletfc 

•r atotmd the Poles, and 
included within tl. & They enjoy too little of 

.'•v pioductiona to 

nn and expand the air, BO as to 

atf'Td him a healthy respiration and a comfortable home, 

ergen, within ten - of the 

n Boas ian fishermen, is the 

me northern limit vf human habitation. Captain 

latitude 

k&k (rf human lift that 

own day tur- 

uklin, of B bold navi- 

doubtleas 

a a sacr • attempting to pene* 

those 1 s. Boti 

1 by the solicitations of 

his I idy Franklin, hare vainly sent out 

to search for him in the Arctic seas of the 

last traces of him \ 

four 

1 t. H and 

••d tic N i;:i;n 

/ the most althy 

and d ■ OS of the human race, laving as 

6f, what num- 
ber of m%Ut in breadth will Torrid Zone to bsl 

fn»rn all tin- r< 
said «-f tl 

of the danger of br*Tiflg the 
HflOfi Oft ■ 1 ZoOttV— 14 What le taid of Ihi '!'• n.ju r.ito 

Zoocef 



116 



THE TEMPEKATE ZOKES* 



we do near the middle of the Northern Temperate, we 
can, in degree, judge for ourselves concerning their cli- 
mate and productions. If the Earth were in form like 
two solid cones meeting at the base, its size would dimin- 
ish in exact proportion to its Equatorial distance ; the 
circle of latitude 45°, the middle of the Temperate Zone, 

fig. 15. 




would then be half the length of the Equator ; but, from 
the globular form of the Earth, the circle of latitude, 
which is half the extent of the Equator, is the parallel 
60°. Of course each degree of longitude at the latitude 
60° is one-half the width of a degree at the Equator ; 
and since a degree on the Equator is 60 geographical or 
69 statute miles, a degree there will be 30 geographical 
or 34^ statute miles. 

15. In taking a general view of the surface of the 
Earth, we are at once struck with some singular coinci- 
dences of conformation in the great divisions of land in 
the eastern and western continents. Each continent comes 
to a point in the Southern Temperate Zone ; each has a 
large number of fertile islands lying- in the Torrid Zone ; 
each spreads to its greatest width in the Northern Tem- 



14. What is said concerning the place on the Earth where a 
circle of latitude is just half the Equator in extent ? What, 
then, does a degree of longitude measure in Latitude 60° ? — 15. 
In studying the Terrestrial Globe, what remarkable coincidences 
shall we find ? 



REMARKABLE MSI 117 

perate; and each • ill northern outskirts into tho 

though the Torrid b the 

Northern Temperate Zone ifl hiMorieally 
v tho most remarkable^ In this alone, 
more land than water. In 
• / oes, — the Southern frigid, — there is no habit- 
and in another, — the Northern Frigid, — 
In the Southern Temperate and 
red by water ia more than 
occupied by land. It ia in the Northern 
heart of the greatest cou- 
th, that • { the human 
Itee an* fi.mid : and th.-n- tho >a\i"iir of mankind made 

n located all the p 

• now, on the western eon> 

-M-.-.-m t<> ■><• ;m, 1 planted a 

. *hoee career has been providentially Mossed, 

just am] t <|ual of 

{i .lit to it> bi- 
ll ' k :.> v • \s > : :;i ai d \irtu.- to lUStain itfl noble in- 
. :10ns, and to recomne nd them I rid. 



rt the Meridian* or 
and I^Atit Min d in ■ n° to 9€ 

MM om of these, ■ degr* < « t~ Latitude ifl always the same, and 
may be estimated in statute mile* at 69 mflei to i degree, I • m t 

f the 
Karth 

owing tat I ihoold I 

]<>rv, *ill f-how the niii: 

! mile j- ■ ;i '!• .'»• ■•• 

• oireaponcln with a minute) on a gr< 
than the aUtut* > 69 : 

• 
Zone*, geographically and historically ? 



118 A CELESTIAL SEMICIRCLE. 

Degrees 
of Latitude. Statute Miles. 

On the Equator 69 

10 68 

20 65 

30 60 

40 53 

50 44 

60 34J 

10 23* 

80 12 

90 

It is important to gain a distinct idea, both on the Globe 
and in the Heavens, of that semicircle of the First Secondary of 
the Ecliptic from which Celestial Longitude is reckoned. Passing 
from one Pole of the Ecliptic to the other, it cuts the Ecliptic at 
right angles at the first degree of Aries, and it is called by As- 
tronomers the First of Aries. The Point where it cuts the 
Ecliptic is that so often referred to — the Vernal Equinoctial 
Point. It here intersects, as we have seen in the preceding 
chapter, both the Equinoctial and its principal Secondary, the 
Equinoctial Colure ; the latter at an angle of 23*°. We hope 
our students have already a distinct idea of the Vernal Point ; 
and will now remember that it is here where the Equinoctial 
and its principal Secondary meets the Ecliptic and its principal 
Secondary, and from which Longitude is reckoned on the Eclip- 
tic from its Secondary, the First of Aries, and Right Ascension 
from the Equinoctial, or its principal Secondary, the Vernal 
Colure. This makes the Vernal Equinoctial Point the most 
important Point in the Heavens for us to understand, as to 
its exact position, except the North Celestial Pole. Having 
found in the Heavens this Point, extend your eye over 90° 
direct to the Pole of the Ecliptic, and the line your eye will 
follow is that of the First of Aries. Observe from the Celestial 
Globe, that Latitude and Right Ascension are the same at the 
Equinoctial Points, but diverge as Latitude and Declination in- 
crease, and are finally at an angle of 23*°, as measured by the 
arc of the Solstitial Colure, in which both the Ecliptic Pole and 
that of the Equinoctial are found. 

On the Terrestrial Globe, learn the parts of the Earth through 
which the Fourth and Fifth Almacantar Circles pass ; review 
their distance from your own position, the Upper Vertex , and 
pay special attention to learning from the Globe the exact loca- 
tion of your Antipodes. If they are in a ship at sea, what is 
their position with regard to the nearest large country and islands, 
and what is their latitude and longitude ? What is their distance 
in degrees and miles from yourself? 



CHAPTER XH. 

i:?,m Sy-tkms. — That 09 tiii: Kartii 
., ma 04 . — Kk.ui ( imii \i An. .Ms ov tiik 

BU I.miuim: \m> I.unoi i i>k i m 90UN- 

LAFBY.— Ol Navk;ation.— Mi :\.\s 09 WKKUIMQ 

l. Spherical System with 

anot: be at their common centre eight 

her their ' incide, or mutually, the 

- with the plane of the 

: in which cast's tin-re will ho 

!i. In ell other oases, 

ol two Spherical 

ms — \i. —will produce 

U fa 

ir will be equal to the 

7 Bgure, by which 
Movable 

1 '. nii.m. nt Positions of the 

j distinguished by 

ight angles. The two 

■ Lane — make the 

m-.l by til-- an- extending from the 

the M rth Pok I o 

this its opjMjsite red on th< 

li Pole to the Nadir, is eqaaL The 
two vertically opposite angles (of equal to 

Chapter XII — l.V. the case* n 

Are pr«nl*. centre b\ 

System with anoth.r — j Draw uckbnard 

figure wit! 
plaoee of the > c u* far as re- 

gards the four first named angles. 



120 



FOTJB EQTJAL ANGLES. 



other), made by the intersections of the two Great Circles, 
are equal to the two first. For suppose the Spheres so 
placed together that the Axes should coincide with each 
other, then the planes of the Great Circles must coincide 
also ; but if the Axes are so moved as to make angles at 
the centre, then the plane of each Great Circle must 
move with its Axis, and just as many degrees. So that 
the two vertical angles made at the centre by the planes 
of the Great Circles will be equal to the two, which may 
be termed Axial, and the four angles are therefore equal 
each to each. Of course the arcs which subtend them 
are equal also. 

Fi£. 16. 



NEW YORK 

o 




6.21U 



MAYlO?™: -T40 A Oft 



3. Although it is more systematic to begin with the In- 
tersection of the Axes and Great Circles, yet in forming 
this union of two Systems into one, it is an angle made 
by the Axis of the one System with the plane of the 



2. What proves that they are equal each to each ? 



OTHER FOUR, Tl 1-. 121 

6r:i . which is tho first-found and 

nt That \gU made ty the 0b9$rv$r'$ 

I the plane of the I } 01 the Am;i,k Of mi: 

i i>: . Tho arc which im-asuivs it on 

which he inhabits is his Latitude 

::ave in t distinguished the arc of tho Lati- 

by a heavier line. 

In the diagram, we locate our Observer at New 
The aw 40° 42' which meafr 

. ni'-MMiivs of course, its oppo- 

led by the arc extending from 
;.tl to the angle of the Lati- 
n ^i the North Pole above 
of the de] 

sion of the South 

:^bt together that 

• he ( treat 
le of th- -then will tl 

be also, since all the angles ai -, the mutual 

coincidence <•: 
Axis ison* 

any number 
of degrees, a- >rth of th«* Eqnft- 

<ede towards the 
south ; and I 

th, toe North Pole will rise 
abov.- the U free. It the Observer, 

the same will be 
4 its 
opposite • togle, th< ion of the sonth. 

6. The angle of Lat! ! it- opposite — the an 

of the elevation <• rth Pole and its oppo 

therefore four angles, all c | u. 1 1 of Latitude, 

: miid am:- 

location of the Ob* 

to tbe Latitude f — 6. How are four angle* | be equal 

eacb to each* 

1 I 



122 GEOGRAPHY FOUNDED ON ASTRONOMY. 

and of course equal each to each. By reference to the 
figure, it is seen that each quarter of the circle has one 
of these four angles of 40° 42', and one of the remaining 
four, each of which must therefore be an angle of 49° 
18', the angles of 40° 42' and those of 49° 18' being com- 
plements each to each. These eight angles at the centre 
take up as their subtenses the whole 360° of the circle. 

T. Terrestrial Latitude and Longitude, in some respects, 
admit of a common description. They are imaginary 
circles which cross each other at right angles, and when 
reckoned in degrees and minutes, they together exactly 
define the situation of any place on the Earth's surface. 
By means of the position of the heavenly bodies, they 
are ascertained with exactness by instruments made for 
the purpose. The Latitude and Longitude of any newly dis- 
covered point on the Earth's surface can thus be determined, 
and its name set in its true place upon maps and globes. 

8. On the sea-coast, the correct situation of the prin- 
cipal capes, bays, and promontories being thus ascertained, 
and the noble science of mathematics lending its aid, the 
boundaries of the sea and land are made out, and exhib- 
ited in their true positions. Geography, that most famil- 
iarly useful of all the sciences, is thus, by means of Lati- 
tude and Longitude, settled on a firm foundation ; and is 
no longer, as in ancient days, involved in darkness and 
obscurity. . . The Baron Humboldt says, it is Columbus to 
whom the world at large is indebted for the knowledge 
of the great truth that the Earth is a globe. Many are 
the navigators who have followed in his track, discovering 
new islands in the deep, which, being correctly marked 
on maps and globes, can now at pleasure be visited again, 
and their products be exchanged for those of other lands, 
for the benefit of all. 

6. What, according to the location of the Observer in the 
figure, must be the degrees and minutes of each of the eight 
angles and their corresponding Arcs ? Suppose the Ob3erver T s 
Latitude was 10° N.,what would then be the number of degrees 
*of each of the eight angles ? — 7. In what respects do Latitude 
^and Longitude admit of a common description ? — 8. Describe the 
<manner in which Geography, as a science, is based and settled on 
$he foundation of Latitude and Longitude. 



AS. I THE PARENT OF NAVIGATION. 198 

9. Thus the great art i ation. by which the 
ooean- barrier has 1 into i broad bighwa 

»ns, owes its useful n<- titude and Longitude. 

tnd maps — made out on a inr.it 

scale, with not only all th< and harbors which he 

oiay and min- 

has all tl * bich would endai 

s and shoals, marked down also. 

10. J mer part of the preceding lesson, we 
Irani what various methods may be devised, by 

mea- venly bodies, to ascertain the 

or ol the eight 
angles of the combined Systems are ever above our Ho- 
und of measuring any on< 

nred ter- 

ur Latitude, cither din 
- q's altitud 
[uinozes, that 
. aitfa dis- 
s Min- 
will be i when in our 

Mer J°, which must tl 

t >r-- be added to the Zenith di-tanee, to obtain our Lati- 
tude : Jolstioe, the same must 1"' sub- 
tract- d the same manner, for l< 

a, add or lubta 
as the ease maj be. 

11. By measuring the altitude of the P 

obtain the measun i thai of our lati- 

. an arc equal to 
our co-latitude. This is I by many ss q 

9. In whit main • 

we lean 

■ 

tt CD-Utit 
Wa*t mu- at the Bo 

Sun • position I At other time*, b«M«le- 

ti..- fi .:, - ... i.r.atioo be add* <. as 1 waea 



•aUracted, from bis Zenii 



124 



STUDY OF THE CONSTELLATIONS, 



the best method of ascertaining Latitude. Or suppose you 
have some bright star on your Meridian, as the upper 
one of the three which compose the belt of Orion, and 
you know that this star is upon the Equator, then if you 
measure the arc from this to your Zenith, it will be your 
Latitude. If you measure on the Meridian the distance 
of the star to the southern Horizon, you will then have 
measured the arc of your co-latitude. These facts show 
the great practical importance of the science of which 
we treat. 



EXERCISES 

On the Celestial Globe review, as you have time, the following 
Constellations and single Stars, and observe their positions in the 
Heavens : 

CONSTELLATIONS AND PRINCIPAL STARS OF THE ZODIAC. 



Names of the Constellations. 

1. Aries, the Ram. 

2. Taurus, the Bull 

3. Gemini, the Twins. 

4. Cancer, the Crab. 

5. Leo, the Lion. 

6. Virgo, the Virgin. 

7. Libra, the Balance. 

8. Scorpio, the Scorpion. 

9. Sagittarius, the Archer. 

10. Capricornus, the Goat. 

1 1. Aquarius, the Water-bearer. 

12. Pisces, the Fishes. 



Names of the Principal Stars and 

their Magnitudes. 
Arietis, 2d magnitude. 

Aldebaran,\. Group { f f£ s _ 

Castor, 1 ; Pollux, 1. 
Acubens, 3. 

JRegulus, 1 ; Denebola, 1. 
Spica Virginis, 1. 
Zubeneschamale, 2. 
Antares, 1. 

/The largest Stars in these 
C are of the 3d magnitude. 



PRINCIPAL NORTHERN CONSTELLATIONS. 



Names of the Principal Northern 

Constellations. 
Ursa Minor, the Little Bear. 

Ursa Major, the Great Bear. 

Draco, the Dragon. 



Names of the Principal Stars and 
their Magnitudes. 

Cynosura, the Pole Star. 
( Dubhe, 1 ; Alioth, 2 ; Benet- 
< nasch, 2 ; Mizar, Megrez, 
( Phad, Merak. 

Kastaben, 2. 



11. What is regarded by many as the best method of finding 
Latitude ? How might the Meridian altitude of a fixed star 
determine Latitude ? 



1.UIS. 



1 •_'.•> 






i of ihf Prtnc:: 

Cxs her 

Camelopa 

Licerta, tl 

Lyra 

na Boreal i a, the B 

B--.:. v tU Berdamaa 
Coma Berenice*, Her 
llair. 

Pagaaus, the 1 rti. 



Priadpd Stars and 
their M 

Sclu-Jir, 3 ; Caj.h, o. 



Dciub, 2. 



"''• / 



'> 1. 
Algenib, 2 ; Algol, 2. 

r^, 2. 

. 1. 

Alphocca, 2. 
I urus, 1. 

r, l. 



- 






.iniu, the 1 
Cash- :»og. 

Hjdra r-serpent. 

Pi*ci- the Soutl 

Argo Xaria, tl rgo. 



Name* of • ,! Stars and 

Magnitudes, 

. 1. 

f fUS99t 1. 

. 1. 

■■ 

; .i, 1. 

Jhaoi, i. 

.9, 1. 



On the Terrestrial t tlio 

principal state*, r: <>untawn, ud 

island* which lie Wti <<r within 

Hm dbtance of 2,070 mile* t> < • : j i your own position. These 

placet r^iny nearest -ituationa bhould bo 
the most minutely understood 

11* 



CHAPTER XIII. 

Great Circles can, by their Planes, be transferred from 
one Sphere to another. — Smaller Circles cannot. — 
Observer's Line and an imagined Ray of Solid Light 
made Mediums for transferring Circles of Latitude and 
of Daily Motion. — Comparative Length of Days and Nights. 
— Right Sphere. — Parallel Sphere. 

1. Our next subject will be the Connection of Circles 
of Daily Motion with Latitude, and the different Lengths 
which the Days and Nights have at different times in the 
year, and in different Latitudes. This subject has a rela- 
tion to that of the Seasons ; but from its importance, and 
its complicated nature, it demands a separate considera- 
tion, — to which the investigations of the preceding chap- 
ters lead the way. 

2. There is, we are aware, a confusion in the minds of 
learners respecting the correspondence of the smaller 
circles in the two Spheres of the Earth and Heavens. 
They are apt to fancy that these circles on the Earth must, 
like the Equator and other Great Circles, each have its 
plane extending to the Heavens, there to mark its cor- 
responding circle. But this is impossible. 

3. The centre of the Earth is the common centre of the 
two concentric Spheres. Every Great Circle of the Ter- 
restrial Sphere cutting this centre, and dividing the Earth 
into Hemispheres, may have its plane extended so as to 
cut the Heavens proportionally, dividing the Celestial 
Sphere also into Hemispheres. In the same manner will 
the plane of any Great Circle of the Heavens divide the 
Earth. But this is not the case with smaller circles. 

Chapter XIII. — 1. How does the author state the subject? — 
2. What supposition of learners is here asserted to be an impos- 
sibility? — 3. How may Great Circles be transferred from one 
Sphere to the other, dividing each proportionally ? 



:.. w-i 127 

led from the Earth lo the Heavens, 
will Sphere, but not proportionally, 

4. Indeed, it' the planet of smaller erodes, parallel to 
Great Circles on the hould be extended to the 

?Mt I ilia] Sphere, they would then 

their Great Circle, — the small 
spae d them vanishing in the distance. Thus the 

n, tangent t<> the Earth, and 
-tance of its whole semidiameter, coincides, when 
srtend< d t«» tii.- Ilnivrns with that <>f the Rational Bo - 
rizon. v >uld this happen, should the pli 

of parallel Alma - 1"' extended, since they 

cannot l»e so far ft :ial Horiaon as 18 the tan- 

In the same manner, if a 

plane tanir-nt t.i the Karth, at the North Pole, weVS 6K- 

oide with the 
plar Squalor. Ma ild the pi 

■ 

ial should they be 

intended to the < Mestial Sphere. 

be shown, that no 
plane of a c 

■•. can \* SUppO* rth. Tak- 

hose plane (it being s Gh 
'i <•♦ n t r» • and marks on its sur- 

i 'irele parallel to 
me toiieh th.- Earth at all, 

• led 1,000 m 
the Earth's - 1 1 « 1 pass at right 

angles to the Earth's extended a\k either north 01 south 

i i<lrnt that in the 

of tu<» Spheres, tl • \ci smaller circles 

in the ot* •. iik- the 

planes g: corresponding to 

Suppose smaller circles of the K> 

,M it be with 



* of the Honwifi, u : relet? 

with tbe Equator and iu para rclea 

of the Celestial , transferred by the extension of thaw 
l to the Terrestrial I 



128 A FANCIED BAY OF SOLID LIGHT. 

themselves. But the Circles of Daily Motion made by 
the Sun, and other Heavenly bodies, are, except when 
they are in the Equinoctial, smaller circles, and yet they 
have their proportional circles on the Earth, and these 
are parallels of latitude. The Tropics, and the Polar 
Circles, too, as placed on Maps and Globes, have their 
counterparts in the Heavens. 

6. We want, then, to find mediums which, extending 
from the one Sphere to the other, shall mark corre- 
sponding circles. These can be found ; but they will be 
straight lines, and not planes. We consider parallels of 
latitude, as originating on the Earth and extending to the 
Heavens, but Circles of Daily Motion, as originating in 
the Heavens, and extending to the Earth. The Line of 
the Observer meeting with the plane of the Equator, at 
the common centre of the two Spheres, makes the angle 
of the Observer's Latitude.* As the Earth revolves once 
on its Axis, the extremity of the Line, the Observer's 
Zenith, would describe in the Heavens a circle there pro- 
portionate to his parallel of Terrestrial Latitude. Sup- 
pose the Observer's Latitude to be 20° : the circle thus 
described in the Heavens would be 20° from the Equinoc- 
tial ; and thus would be transferred a smaller circle from 
the Earth to the Heavens. 

7. The apparent path which the Sun, or any other 
heavenly body, describes in moving through the Heavens 
during one rotation of the Earth on its Axis, is its Celes- 
tial Circle of Daily Motion for that day* In order 
to obtain a correspondent Terrestrial Circle, let us con- 
ceive as coming from the centre of the heavenly body a 
ray of solid light (since light moves in straight lines), of 

* That is, meeting with a straight line drawn from the Earth's 
centre to the Meridian, on the plane of the Equinoctial. 

5. Do corresponding smaller circles exist, however, on the 
two Spheres ? — 6. How can we find an imaginary line which, pro- 
ceeding from the Earth, may be supposed to mark the smaller 
circle of the Observer's Latitude on the Celestial Sphere, as the 
Earth revolves on her axis ? — 7. How may we fancy a line which, 
coming from the Celestial Sphere, shall mark on the Terrestrial, 
as it daily revolves, any heavenly body's Circle of Daily Motion ? 



. Ui 09 daily tf&l ; 
miffi (he Earth's 

asBfce. This lino of li_;ht. wh.-ro it int.rs.vts (he Ivirtli's 

I mark, as the Earth revolved <>n its axis, the 

Tfm-strial Cirrl«> of th«' I>aily Motion of the lx-avmly 

bodv rhich it ] L The Terrestrial ( 

I upon toe Earth's rarfaoe, would be that 

d< b ribing it 

tall. 

8. 1 star, >1 tral rav of solid light 

[}\\\< mark its lino Of daily motion, 

. be invariable, since both tli and 

Bxed ( hring tp the 

imrnon^' Sxed Btare, they appeal in the 

] ■'. ,i -. - wii.n \i.-\\.-d fr< -m opposite parti of the 

Earth's orbit By th< annual motion, however, 

i^^cribe a jearly circuit, though their 

the tame. l»ut the Sun, u * e 
have seen in I e Seasons, ha vim: Ui ■] 

opposite 284* south, 

traverser I 8 I at to 
the o 

9. 5 does, tho 

unlike tl 
will, on each succes>; ; -' m a different pari of 

■ • pari of the Earth* 
ree the 
■ return ; 
• is, thre« in which to make 23j° distal 

al.Miit L6 minutes a 
Hit course- . like a b d screw, 

*e threads are close to each oil 

J at noon to any Observer whea 
his Circle of Da 

What would the circle described be in regard to thi fa 
enlj bodv wbote central rav do* 

rrr. ark. i . • tfei Cardm of Diulv Motion of the Fixed Start I In 
'; ret pect 

i of the Fixed Start 1—9. Deter. >ailj 

i during a year. 



130 



A VERTICAL SUN. 



Observer's Latitude, and at no other time. The accom- 
panying figure represents an Observer whose latitude is 

Fig. 17. 




23^° north, having on the day of the Summer Solstice 
the Sun in the Solstitial Point, on his Meridian. A Ray 
of Light supposed to proceed from the centre of the Sun 
will coincide at this day with the Line of the Observer ; 
and these two lines being, by a revolution of the Earth 
on its axis, made to describe correspondent circles on the 
two Spheres — the Observer's Zenith in the Heavens, and 
the Sun's central ray on the Earth — there will be circles 
both of the Observer's latitude 23J°, and of the Sun's 



10. Draw the figure and explain from the blackboard how the 
imagined central ray of the Sun's light has marks on the Terres- 
trial Circle of the Sun's Daily Motion, or his vertical course over 
the Earth at a specified day — viz., the 21st of June. 



DITJRNAL CIRCLE OF A STAR. 181 

lad in t: 'hese 

lines will r must on that 

Sun in his Zenith. And to en ry 
Observer in tl his will bo the case, tnd fa 

other; for in no i the Earth on this day will 

ion be identical with the 
Obs 

11. gined 1 I solid light will 

apply to the card heavenly bo 

uinoctial, lei us take a ^tar d, 
in tl. - here, whose d from the Zenil 

43°. T Latitude, i 

mak»- ti N thern Dechn 1°, and its Polar Dis- 

tance 23^°. We will imagine our line of I 
through p to ' !aiib revolves, toe 

describes 

• 4 light from 
its centr* 

eoneipon- _r rrle from r to o. This circle in the 
Beam m b the diornal « iide of die star at d, and tta eor- 

i: i«'ii 
of the stars r 

ticai ; fall in I per- 

petu . D this case fcreret mark upon the 

k 
aee of the stir at d is, as seen on 
the diagr latitude of the 01 

: ! »wer 

cull: 

star is equal to < 

it be towards the elevated Pole, it never sets ; 

the depressed never rises. I v be seen 

the diagram, by the star at b, the same bom tho 

11. Draw on tho blackboard and dencr »iilj 

Motion of a Star whr*e Zenith Distance U 48°, ar 

of a 
■ 
.: Start in your ial Appa- 

rition \ of Perpetual Occulta: 



132 DITJftNAL AKD NOCTURNAL ARCS. 

Southern Pole, as is the star at d from the Northern. 
Stars which never set describe Circles of Perpetual Ap- 
parition, and are Circumpolar Stars ; those which never 
rise, describe Circles of Perpetual Occultation. 

13. Every Observer has all his Circles of Daily Motion, 
except those of Perpetual Apparition and Occultation, 
cut by his Horizon into two parts, upper and lower. So 
far as the Sun's light is regarded, the upper is the Diur- 
nal and the lower is the Nocturnal arc. Since the Sun's 
presence causes Day, and his absence Night, no arcs but 
such as he traces in the Heavens can, with the same 
propriety, be called Diurnal and Nocturnal. When the 
days and nights are equal to any Observer, then his Ho- 
rizon cuts the Sun's Circle of Daily Motion into two 
equal parts. This can never be except at the Equinoxes, 
when it coincides with the Equator. The greater his dis- 
tance from the Equator, the greater will be the difference 
between the Observer's Diurnal and Nocturnal Arcs, and 
the reverse, 

14. This may be understood by Fig. 18, in which we 
see that the Horizon, h o, cuts into equal parts, e q, the 
Equator, and into unequal parts the Circles of Daily Mo- 
tion, d r f and abc. In this diagram we give the Ob- 
server's Latitude at 40° north, the Sun's Declination at 
20° south, and the hour, noon, when the Sun is on the 
Meridian. Our imagined line of solid light will, by the 
rotation of the Earth, mark on this day on its surface the 
Circle of the Sun's Daily Motion, abc. As much 
shorter as is the arc a b than the arc b c, of which a b 
above the Horizon is the Diurnal, and b c below the Ho- 
rizon the Nocturnal Arc, so much shorter will be the 
day of the Observer (under z, the Zenith) than will be 



12. How is it with Stars near the South Pole which are equal 
to or less than your latitude? — 13. How does your own Hori- 
zon, or that of any Observer, cut all his Circles of Daily Motion, 
except those of Perpetual Apparition and Occultation ? To 
what are the terms Diurnal and Nocturnal Arcs applied ? When 
the Observer has his days and nights equal, what occurs ? Which 
has the greatest difference in the length of his days and nights, 
the Observer in 10° of latitude or in 20° ? 



: n v. 







D nation of 
had imc i 
raid then have been loi 
than i€ differen d q 

\ n :m«] I 
f the same figure, it m apparent, 
that lay and night «rill be 

equal, when I idei with the 

to the fij difference the two 

diurnal arcs do and a b will be seen to be l o -f- d m. 
l q ; since lo=bn. 

Draw on I 
onr imagined 1 

old describe the Ob*er\ uily Motion I ;de 

I the duo's declination being giv 
12 



134 LET THE EYE BE EDUCATED. 

of Daily Motion — that is, at the Equinoxes ; and that in 
all latitudes where the Sun's Circle of Daily Motion is 
nearer to the Observer than the Equinoctial, his days will 
be longer than his nights ; but when it is farther, his 
days will be shorter than his nights. Although the Ob- 
server {Fig. 17) is only 23^° from the Equator, and the 
Sun is in his Zenith, so that he would cast no shadow to 
the north or south at noon, yet his diurnal is longer than 
his nocturnal arc, and his days are longer than his nights. 



EXERCISES. 

In order to educate the eye of the pupil to judge of distances 
in the Heavens, let him learn, and looking at the Heavens and 
pointing to the stars mentioned, say aloud or mentally : 

From Merak to Dubhe is 5°. 

From Dubhe to Megrez is 10°. 

From Dubhe to Mizar, 20°. 

From Dubhe to Benetnasch, the whole extent of the Dipper, 
25°. 

From Caph to the Pole Star, 30°. 

From Lyra to the Pole Star, 5C°. 

From Megrez to Caph, 60°. 
Remark that the degrees mentioned are degrees of a great circle, 
not degrees like those of Celestial Longitude and Right Ascen- 
sion, which diminish till they vanish at the North Pole and the 
Pole of the Ecliptic. 

Remark, further : these distances, in some cases, lack a little 
of absolute correctness. Lyra has 38-p of northern declination, 
which makes its Polar distance 51^°. The distance of the Pole 
Star from the true Pole of the Heavens is about 1^° towards 
Caph. JSow Caph is about 31 4° from the true Pole, but is 30° 
from the Pole Star. Megrez has the same distance as Caph from 
the true Pole, but is a little farther from the Pole Star; and 
thus the distance from Megrez through Cynosura to Caph is a 
little more than 60°. 

Lyra's position it is highly important to know. Our students, 
in learning our plan of studying the Heavens, will never be at a 
loss to remember the Vernal Colure on the Caph side of Cyno- 
sura, and the Autumnal Colure on the Megrez side of that Pole 

15. Suppose the Sun to have had the same degree of northern 
declension ? Show from the figure the difference between the 
Diurnal and Nocturnal arcs. (Observe the note.) 



RIGHT, OBUgt'K, ANi> 1AKMI1I. 135 

and iheu all know that th 

; t he 
■ Wmtei 
iii it H the Pole of the 

m of UranographT. 
tiful lonely .-tar. the brig 

of the Pole of tho 

It" l.\ ra l- not to I>o seen— foe 
being a li" perpetual apparition, it will, 

thou l»e absent — yon may then know that tho EeliptlO 

r 1 m mi Bo* 

• oed end located by 

I shall rind the Winter Colore to the wee! of the 
aL 

diyinoni <>f land and 

- breadth, 

in your own is 

lee do the 

nrot and teco nd of these Almacantar 2a fhnp- 




SAPTBB xiv. 

JL 1 - . l Pan it rat, fl 

— The Atmosphere — ETnOHi j 

ft — AeRJAL TlDBi. — Ocea 

1. Of the I ' ith 

I juth, t)i* • different modal ; pfo- 

MCMud, an ' 

■ in- 
:' these three Bph< 

Alth of the world 

profitable t<» take 
the view here indicate i. undent 

ing the various poeiti »* Observer, an d I 

CnAfTER Of what Sy-' 

•peak I Of what U 

remarked of tho rendence of mankind in regard U) then Bye- 
it 



136 



A SHADOWLESS OBSERVER. 



upon the influence of the Sun and the appearance of the 
heavenly bodies ; for if, comparatively, few live on the 
Equator, and none at the Poles, yet the intermediate sta- 
tions approximate in condition, according as they do in 
place, to the one or the other. 

2. When the Observer's System so intersects the Earth* s, 
that, mutually, the axis of the one lies in the plane of the 
Great Circle of the other, his place is in a Right Sphere. 
This is one of the two cases in which the central angles 
of the Intersection of the two Systems are four Right 
Angles. All the dwellers in this Sphere live on the 
Equator, and, of course, under the Equinoctial. 

3. The accompanying figure shows the Observer in 
a Right Sphere. The dotted lines represent the Axis and 

Fig. 19— A Right Sphere. 



SP 




£ Q 



Great Circle of his Movable Positions. They here coin- 
cide with the firm lines which represent the Permanent 
Positions of the Earth's System ; the Axis of the Earth 
lying in the plane of the Horizon, and the Observer's 
Line in that of the Equator. This figure represents the 



1. Why, since mankind mostly live in one, is it worth while to 
pay attention to all of these three Spheres ? — 2. When is the 
Observer's place in a Right Sphere ? Where are all the people 
who live in a Right Sphere ? — 3. Draw and explain the diagram 
of the Right Sphere, recollecting the use of the dotted lines. 



. and the time of 

•jotli uf March or the 23d of 

nly (the Equii 

• daily motion coincident with the Gqoa- 

j i the Sun's central merid- 

with the ( H Line, and m 

ril ray will mark on the Earth 

\ nith will describe in the 1 1 

rti Bight Sph 

because all ! . whether of the 

make p ith his Eori* 
v. i irth'a motion on its 

thai "Observer from hu on, aa seen in 

■ 

nent 
will t*> • (ue to the Mend 

will be seen \ irele 

1 tiurnal and 

alway* eqi 

—an his Si itarry II sty 

n ill present itself to his i i< 

■I on the Equator, 
be the largest po- • r it has diminished as it 

has receded towards the Poles, I i l< * • that <h-<riU«l hy tho 
m or the Northern Bear. The Polar S 



nith ? 
—4 ■ pheret II 

may 

■ 
Meridian, what wiil ootocidc With I; What fttars will 

be Twjbl. 

12« 



138 



AN IMAGINARY OBSERVER, 



Cynosura rests quiescent in the Northern Horizon with- 
out a mate at the South, and this Observer has no Cir- 
eumpolar Stars. The Observer on the Equator is in the 
only true position on the Earth's surface, with regard to 
the Points of Compass. Here alone the positions of the 
Movable System do not, in this respect, conflict with those 
of the Permanent. 

6. The Parallel Sphere constitutes the only re- 
maining case where, in the Intersection of two Spherical 
Systems, there are four right angles at the centre. 
When the two Axes coincide, and also the planes of the 
two Great Circles — viz., the Observer's Line with the Axis 
of the Earth, and likewise the plane of the Equator with 
the plane of the Horizon — then the Sphere is said to be 
Parallel. 

Fig. 20.— A Parallel Sphere. 
a; p 




*l. We have represented the parallel Sphere in the ac- 
companying diagram, where e q, the Equator, is parallel 
with h o, the Horizon, and the Observer's Line with the 
Earth's Axis, as may be seen by the double line, one part 
dotted, which in our figures always represent Movable 
Positions. The Sun in the United Horizon and Equator 



5. How do the Points of Compass appear to the inhabitant 
of the Equator ?— 6. What is said of the Parallel Sphere ? — 7. 
Draw the figure, and explain the position of the Observer in the 
Parallel Sphere. 



POLAR ATI IS. 

indicate 

Our Observer here bio ; for we know do! ih.it any 

.1 human beil 

• of the II- ■< 
\ rthern Eennsphere are, for 
six mod _ their perpetual circles of daily mo- 

9tar, fixed in the Zenith ; n<>r 

whether any jht, and 

i seen th- s >un appearing in the 

Horizon — wheeling as he rises, and rising as he wheels — ■ 
perform i- rly parallel to 

the n ■'. that in three months he 

ling for a few da] 
n hia immense spiral 
for a —till at the Autumnal 

I again i: I iarth and 

Twi- 
: lasts two in- 
to the cold hr 

ns of 
the 

8. The gn Pwi- 

in the 
not yet 1 
Mo*r Earth, A 

interrupt our 
All 

Earth and the -which <!•> m»t produ 

angles a* 

I th«^e are all cases wh< 

!itre, as I 
eompreh 
the gr^r balk of mankind 

who reside l» 1 the Poles, we shall, 

though not im tin- Nib 

^h»t is m ijlpearanr < ar- 

•rir bodie» in a Parallel Sphere ?— 8. When k tho Sphere said 
to be obliq*4 f 



14:0 man's fiest necessity* 

9. Both the heat and light of the Sun are modified in 
a manner greatly beneficial to man by the Atmosphere 
or Air, which surrounds the Earth, rising above it, to a 
height varying probably from 35 to 50 miles. The At- 
mosphere is the element in which Man exists by respira- 
tion. There must be lungs to breathe, and air to be 
breathed, else animal life does not begin ; or having be- 
gun, it ceases. And there is no more important rule to 
direct us to use means for our physical well-being than 
this, that the more perfect is breathing, the more vigorous 
is health ; and the reverse. 

10. All animal life is thus sustained by Respiration, — ■ 
a term which implies the existence of atmospheric air, and 
its reception by lungs. Animal heat is produced by the 
union of the oxygen contained in the Air, as it chemi- 
cally combines, in the way of animal combustion, with 
the carbon of the blood ; which is derived from the ali- 
ment — viz., the water and the food — taken at the stomach. 

11. Animals are said to have a great quantity of 
breathing when they consume much Air. Birds have 
much breathing, and consequently great animal heat and 
a rapid circulation of the blood. Fishes, whose gills are 
imperfect lungs, which obtain no Air, except from the 
small quantity contained in water, have, on the contrary, 
so little animal heat, that they are called cold-blooded 
animals. They would not be animals at all unless they 
breathed. " Respiration," says the great naturalist, Cu- 
vier, " is that which animates,'' or constitutes a being an 
animal. 

12. The atmosphere is commonly defined as an elastic 
fluid. By its fluidity its particles move easily among 
themselves, and by its elasticity they may, by external 



9. What is here said of the Atmosphere ? How does the im 
portance of the Atmosphere in regard to man appear? What 
rule important to health and life is here laid down ? — 10. What 
is said of Respiration ? Has animal heat any connection with the 
atmosphere ?— 11. When are animals said to have a great quan- 
tity of breathing ? * What difference is noticed between birds 
and fishes ? Are there any animals which do not breathe ? — 12. 
How is the atmosphere defined ? 



TABIABI ITY. 141 

ple a su re, be diminished in volume, and made move d< 

pitSBUTO is removed, spring a^ain into 

largo balk Heat expands and coldness condenses air; 

! afied it. The atmosphere 

ttion. Being adjacent to the Earth, 

in flying off into the 

the nearest particles gravitate most 

- them b< An.l this >u- 

by the pressure of the superin- 

oambert : so that the density of the air is 

grea* and rapidly diminishes as wo 

,t of any assumed column of the 

atm i ! trtli upwards, is equal to a column 

of « |ual base, and of the altitude <»f :i-j?, \<>r <»f 

a oolumi. In Pomps and Hy- 

:r . iken off from 

a the 
I 

md the mercury I 

M - of 

the atm the tops of in 

diiri • ; and trawl- 

. in ascea : up in balloons, Bnd 

In as- 

ceo<i \ir will hare lori one-thirtieth 

of its w. 10,000 feet, one-third ; 

rons to I- 



What 

c«u* . ve a great 

Um Earth* nurfao I • I eotamfl i 

Atmoephere a- 

liet aa the dist.t 

foaod suiuhk for lesuiistiuu I v. 

Air loses ooethn tit th of iu weight t oi nebalf ? 



14:2 TIDES OF THE AIR. 

especially when the change is made suddenly ; and in 
ascending still higher, a region will be found where the 
atmosphere is too rare to support flame or animal life. 

15. Owing to the diurnal rotation of the Earth, the 
atmosphere is higher in the Equatorial regions than at 
the Poles, and is therefore, on its outer surface, still more 
spheroidical than the Earth itself, whose denser material 
would not, like air, readily yield to the operation of the 
causes of a form which is believed to be universal among 
the planets — that of the oblate spheroid. 

16. Were the atmosphere to be free from all causes of 
the motion of its particles among each other, it would 
become unhealthy from stagnation. The same remark is 
applicable to Water — that important element which, 
next to Air, is the object of man's most imperative neces- 
sity. Air and Water are in their nature connected, and 
being agitated together, as in storms of Wind and Rain, 
they mutually purify each other. Air, like Water, is also 
kept from stagnating by the attraction of the Sun and 
Moon, especially the latter ; by means of which there are 
Aerial Tides. By the Tides, as will hereafter be ex- 
plained, the whole of the particles of both the Air and 
the Water which surround the Globe are every day moved 
throughout their entire masses. 

17. Water covers more than two-thirds of the surface 
of the Earth ; but this proportion is none too large to 
give the greatest possible amount of arable land. For 
land not suitably watered, by running streams, by rains 
and dews, is nothing but a useless and hideous desert, 
without life, either animal or vegetable ; and wherever 
these are interior parts of vast continents which cannot 
be watered — such deserts are found ; as in the heart of 
Asia, Africa, and North America. The Ocean is the 

15. Where is the Atmosphere the highest ? What do we sup- 
pose to be the form of the Atmosphere ? What is believed to be 
the form of all the planets ? — 16. In what case would the Atmo- 
sphere become unhealthy ? What is here said of Water ? How 
do Air and Water mutually purify each other ? What beneficial 
effect of the gravitation of the Sun and Moon is here noticed ? — 
IV. What proportion of the Earth's surface is covered by water? 



OCEAN CAVES AKD MOtTNTAIKS. 1 I > 

grand reserv< 8 

raises th- : - and the atmosphere i 

and condenses their minute particles Into clouds; — by 
v them up — by the agitation of its 
i in rain, bail, and snow upon the 

[mnA '1 

na, rast quantities fall there, so th.it on their 
oil wamm id deep lakes are kept 

oaand streams which, Bow- 
>me confluent in the 
vail' • 1 thus cany their waters bach to 

the Ooeai ?er the land 

16 
ssjrfbos as the land. The t--]^ ft' oceanic mountains ap- 
pear as n mountain i 

ted with 
nenta. Such 
are * 

greatest depths of 

fifth ; ar 

s 

low its l iv he to 

the ; the same, in about the pro- 

:• to that 

celebrated Lieut. M.ui.y, 
of Wa-hii.jt "J.. 



iwn have we to suppose 
r i» none too great for the ^o< < ir- 

calating water- 
Ocean raised f How do they be< 
do they fil 

and how doe* this cooduco to th« —18. 

What it said of the In 
top* of Oceanic mountain* appear I V< 

Oceanic mountain* • Lat is aaid coo- 

; the depth of the Ocean ? 



144 CULTIVATE THE IMAGINATION. 



EXERCISES. 

We hope our learners will by degrees acquire the power of so 
controlling their minds as to make truth in Astronomical Geogra- 
phy seem truth. We know that we live not merely on an out- 
stretched plane of land and water, with a blue dome above us, 
but upon a convex Globe, with an apparent concave sphere on 
every side, studded with stars. And we know that the circles 
concerning which we have been studying, and which belong to 
the two Permanent Systems, can only half of them appear to us 
at once. Let us, when we see what is above our Horizon, exer- 
cise our minds to locate, in imagination, their counterparts be- 
low. 

After having prepared ourselves by the previous examination 
of the Globe, let us go forth and study the stars. Let us point 
with one hand to the North Pole, and keeping the two arms in 
the same straight line, point with the other hand to the South 
Pole. Point next to the North Ecliptic Pole, and then in the 
same manner to the South. We know that beyond the convex 
Earth, which is between us and the opposite Heavens, is the 
Concave Celestial Sphere, and we see it in fancy, if not in real- 
ity. Then, with your eye on the North Ecliptic Pole, point to it, 
and keeping your finger pointing the same distance from C}'nosura 
(23£°), move it around that Polar Star, and you will have 
pointed out the Arctic Circle in the Heavens. Perhaps you 
already know from the Globe the stars through which it passes. 
You know of course that it is about 7°, nearly one-quarter of 
the distance nearer the Pole than are Caph and Megrez. Then 
turn to the South, and shutting your eyes, and thinking of the 
stars below, move your finger as if you traced out the Southern 
Polar Circle of the Heavens. The bright Southern Cross and 
the Centaur will perhaps seem to be where they are — a few de- 
grees north of the Antarctic. Their circles of daily motion, you 
know, are circles of perpetual occultation, as those at the north 
are of perpetual apparition. Still they are in the Heavens be- 
yond the Earth. There they have an actual existence in the 
celestial places towards which you point. 

In the same manner follow over the face of the sky (first 
reviewing, if necessary, the Celestial Globe), and notice the 
principal^ -constellations through which pass the Northern and 
the Southern Tropics, and lastly the Equator, carrying these 
circles around the Earth, by sight, above your Horizon, and by 
imagination beneath. 

The Northern Tropic in the Latitude of New York is 15 hours 
above the Horizon and only 9 beneath. The Equator bends 40° 
north of your Nadir below the Horizon, as it does 40° south of 
your Zenith above. Of the remaining distance (50°), the Tropic of 
Cancer takes 23|° ; so that for the northern limit of that Tropic 



i: MADE AVAILAIUK. 145 

below the Hoi:. .t within 26^° of yon B 

learn tho third Almacanttr /■ 
1 Almacantar Circle, which 
j to 6,210 miles from 

• . , Qfl Of land 

iog the pointa of compass in 



CHAPTER XV. 

HON. 

I. L ifl Ml rvatimis 

without regar r,tbeirlabon 

■ consent, all stial 

ei m if u and thai point 

in a posit 
som* t from thai whi< 

idled the 
in the B riaon, it. 
d ill- Horizon 
th« / 

Earth, v the 

in four differ- 

:ital, and the 
( «iles- 

iirht lines— would 



■ 



146 




appear in the Celestial Sphere at r, while to the Observer 
at the Upper Vertex, it would appear at s ; lower than r 
by the arc r s. This arc is then the measure of the differ- 
ence between the true and the apparent place of the Moon 
in the Horizon, and it is therefore the arc of the Moon's 
Horizontal Parallax ; and the angle which this arc sub- 
tends, r 1 s, is the Angle of the Moon's Horizontal Par- 
allax. 

3. Between the Horizon and the Zenith, the heavenly- 
bodies have a Parallax of Altitude diminishing as the 
altitude increases, until at length it vanishes in the Zenith. 
The parallactic angle and arc, when the Moon is in the 
second position, are less than in the first, smaller still in 
the third, and are nothing in the fourth ; the Observers at 
the Centre and Upper Vertex having then the same line 
of vision. The Horizontal Parallax of any heavenly 
body is , therefore, its greatest Parallax. 



2. Draw on the blackboard and explain Fig. 21. — 3. Where is 
Parallax the greatest ? — How is Farallax affected by increase of 
Altitude ? 



rm 1 17 

IBJ li.\'iv.'iilv 
its Par ill ix. Bup] I ; 

i will be leas than th 

for w the line of vision from 

ing that from 

(which of course lies in the 

ill !••' less than the 

ual angle (suppose the 

less, and the cor- 

In the sam.' manner 

and the angle of 

. until it 1mm ornes quite im- 
i ". 
i any other heavenly 

Pot 

in t ; • tn the 

made by 

a right 
bo many degrees 

i r 1 B0°. In this 
midiamet 
es. The eing 

remainii 
ran !-• bund, and one <-t* th.-.- si.j.->, <■ 1, i> tin* M«»« >n'- dis- 
tance from t). known to be :M< 1,000 
i 

irenly body is as 
i!i'i:i\ .|.-jr..- a:-.\.- the Borisoa aa it- measure on a v.-r- 

nmal be made on ac- 

FaralUx » readme i* 

ri7."ijtal Parallactic nteet poa»: 

ut ut* in an^le I E the 

fljrure the triangle i I general rule conccruiog 

'jwtioo of a heavenly body f 



148 HOW WE SEE. 

count of Refraction as well as Parallax. Refraction 
refers to the nature of light and the laws of vision. 

7. We see by means of rays of light which ordinarily 
proceed in straight lines from the objects of vision to the 
eye. The eye sees those objects in the direction of the 
ray which last enters the eye, and at the distance of the 
length of the ray. Thus, in general, nature teaches us to 
regard the objects of sight in their real positions. But 
for wise ends the Creator has given to light the properties 
of Reflection and Refraction, by which its blessings are 
multiplied ; although by their means objects appear out 
of their true places. 

8. Light, in passing through certain transparent sub- 
stances, such as glass, water, and air, has its rays bent. 
This bending of the rays of light, as they are coming to 
the eye from bodies which are seen through these trans- 
parent mediums, is termed Refraction. If you place a 

Fig. 22. 



staff obliquely in a vessel of clear water, it will appear 
bent, and the bottom of the staff nearer the upper surface 

6. What exception is to be made ? To what does Refraction 
refer ? — 7. By what means do we see ? In what direction are ob- 
jects seen ? At what distance ? By what properties of light do 
objects appear out of their true places ? What good purpose is 
thus effected ?— 8. When is light said to be refracted ? What 
illustration is given ? 



REFRACTED RAYS. 



149 



of the water than it really is. If you place the staff per- 
pendicularly, there will be no refraction. 

9. The more dense the medium, the greater the Re- 
fraction, and the reverse. Now, the atmosphere which 
surrounds the Earth is a transparent and slightly refract- 
ing medium ; — more and more dense as it comes nearer 
and nearer to the Earth. On account of this, all the 
heavenly bodies are seen by rays slightly bent downwards 
as they enter the atmosphere, and curving more and more 
as they proceed to the eye ; so that they thus appear 
above their real places. The Sun is thus seen above the 
Horizon after its body is really below, which makes the 
day two or three minutes longer than the night. The 
angle of Refraction grows less and less as it approaches 
the Zenith, where it is nothing. 

10. This is further illustrated by the appended figure, 

Fig. 23. 




in which e s represents a section of the Earth's surface, at 
the upper vertex of which stands our little Observer ; but 
here we have placed his feet somewhat lower than usual, 
because for our present purpose his eye must be in the 



9. What is said of the atmosphere in reference to Refraction ? 
How is the Sun's appearance affected by the Refractive power 
of the atmosphere? — 10. Draw and explain Fig. 23. 

13* 



150 SUNLIGHT PROLONGED. 

plane of his Sensible Horizon, h o. Since rays of light 
are not bent by Refraction when they enter a denser me- 
dium perpendicularly, the Observer will see the Sun in 
his Zenith in his true place, by a ray of light which 
comes direct. But suppose the Sun to be in the station 
most distant from the Zenith of the three stations on the 
figure, he will see the Sun in this case above the true 
place, and as being in the station next above. For he sees 
him by a bent ray, and in the direction of the ray which 
last enters his eye. If there had been no atmosphere, 
the Observer would have seen the Sun by a ray which 
would have come direct from the Sun to his eye. With- 
out refraction, the ray s A, by which he now sees it, would 
not have come to his eye, but would have passed above it 
and proceeded to l ; or had it been only refracted at a as 
it entered the upper layer of the atmosphere, it would 
have passed to n ; but by continued refractions it forms 
the curve sabc, and this entering the eye in the direc- 
tion b c, that direction is, by the laws of vision, followed 
by the Observer's eye to the distance of the object, and 
there the Sun appears above his true place. The arc on 
the Celestial Sphere between the true and the apparent 
place of a heavenly body is the arc of Refraction. 

11. Thus we see that while Parallax lowers the true 
place of a heavenly body, Refraction elevates it. The 
astronomer must, therefore, in order to find the true place, 
subtract the arc of Refraction and add that of Parallax. 

12. We have seen that Refraction, operating by certain 
properties of the atmosphere, has an effect to increase 
and prolong the light of the Sun. Reflection has per- 
haps still greater influence in multiplying the blessings 
which we derive from that king of terrestrial glory. It 
is by the Reflection of the Sun's light that all opake 
bodies are known to us by sight, that the Moon cheers us 
by her milder radiance, and Venus shines forth in beauty, 
the star both of the morning and the evening. But 



11. In what respect have Parallax and Refraction opposite 
effects? — 12. "What effects are produced by the Reflection of the 
Sun's rays ? 



TWILIGHT — 18°. 151 

especially for the mild dawn of the morning and the calm 
twilight of the evening are we indebted for the reflection 
of the Sun's light, as it falls upon the denser particles of 
the atmosphere below the Horizon. The last ray which, 
by the united powers of Reflection and Refraction, in- 
fluences the sight of the Observer, comes from the Sun 
when he is 18° beneath it.* Twilight under the Equa- 
tor continues an hour and twelve minutes; since 15° 
of space (it being a Right Sphere) equals an hour of 
time, and 3° equals 12 minutes. But as the Observer 
goes from the Equator towards the Poles, the Sun's line 
of daily motion becomes more and more oblique till, in 
latitude 49°, within 18° of the Polar Circle, twilight at 
the Summer Solstice continues all night. Since in a Par- 
allel Sphere, the descending Sun is three months in reach- 
ing his lowest point, after going below the Horizon, which, 
as the Equator and Horizon are here coincident, is 23^° ; 
then as 18 is to 23 J will be the proportion of that three 
months which will have twilight after the Sun descends 
and dawn before he rises. 



EXERCISES, 

Our last exercise was one in which we hope our learners took 
pleasure ; and if so, it is evidence of improvement, for it was a 
bold lesson, and one on which we would not have ventured at 
first. But it is easier to learn whole circles than half ones, and 
incomparably more profitable. This you will more plainly see 
as you pursue Astronomical Geography. And who knows but 
you may yet travel South, stand on the Equator, and see 
all the stars alike to both Poles. Or perhaps you will advance 
into the centre of the Southern Hemisphere, and with your own 
eyes see the constellations there, making their perpetual circles, 
while those of the North will then have to be imagined. In 

* The Quadrant of Altitude, when fastened to the Upper Yertexof the Ter- 
restrial Globe, extends 18° below the Horizon to show the extent of twilight ; 
so that in any latitude it is easy to find it. 



12. What is here said of twilight in a Right Sphere? in Lat. 
49° ? in a Parallel Sphere i 



152 VIA LACTEA. 

such a case of Southern residence, you would see some black 
spots of the sky looking almost as if the blue vault had aper- 
tures through which your eye penetrated into the profound 
abyss of immeasurable space. These spots, which are not yet 
understood, are called the coal-sacks. There is also to be seen 
in the Southern Heavens another unexplained phenomenon. It 
is a pyramid, faintly luminous, called the Magellanic Light. 

Observe now in the Heavens and on the Celestial Globe the 
Galaxy, or Milky Way. It is an interesting part of the Celestial 
Sphere, and is especially considered as such, since the elder Her- 
schel discovered by his great telescope, what has since been con- 
firmed, that its cloudy white or milky appearance is the effect 
of an innumerable congeries of stars, too distant for our unaided 
vision separately to contemplate. This great Zone of the Heav- 
ens surrounds the Earth; but passing below our Horizon to 
the South into what is to us the region of perpetual occultation, 
we can never see its Southern portion, but we must imagine it. 
In studying the Milky Way on the Celestial Globe, let us con- 
sider it according to its general form, which is that of a great circle of 
the Celestial Sphere. Let us first find its extreme northern and 
southern parts. These will be found — the northern in Cassio- 
peia, near Caph, and the southern in the Southern Cross. Place 
these two points in the Northern and Southern Horizon of the 
Celestial Globe, and the general course of the Milky Way will 
then be nearly coincident with the Horizon. It will be seen 
that at its greatest (northern and southern) declination, it crosses 
the Equinoctial Colure (at the north the Vernal, and at the 
south the Autumnal) ; so, at its intersections with the Ecliptic 
and the Equator, it crosses the Solstitial Colure. 

On the Terrestrial Globe, continue the study of the Alma- 
cantar Zones. Learn what lands, seas, great rivers, mountains, 
and cities the Fourth Almacantar Zone contains, and remember 
that their distance from your own position is from 6,210 miles 
to 8,280 miles. Which of the Almacantar Zones have an equal 
number of square miles ? 



CHAPTER XVI. 

The Moon. — Its Poetic Influence. — Size.— Position. — Three 
Motions. — Orbit. — Selenography. — Nodes. — Gravitation. — 
Tides. — Light of the Moon. — Eclipses. 

1. An infant who had just begun to utter single words, 
joyfully exclaimed, as he saw the full Moon rising, 
" Lamp ! lamp !" The transport of the child was poetic. 
All poets love the Moon — especially when they are sad 
and sentimental. Thus Burns : 

" thou pale Moon, that silent shines, 
"While care-untroubled mortals sleep ! 
Thou seest a wretch, who inly pines, 
And wanders here to wail and weep." 

2. The great Milton, however, who never suffered him- 
self, though utterly blind, to "bate a jot of heart or 
hope," thus describes the Moon, with the other heavenly 
bodies which bedeck the evening sky : 

"Now glowed the firmament 
"With living sapphires ; Hesperus, that led 
The starry host, rode brightest, till the Moon, 
Rising in clouded majesty, at length, 
Apparent queen, unveiled her peerless light, 
And o'er the dark her silver mantle threw." 

3. By Hesperus is meant the planet Venus, the bright- 
est star of the Heavens. This planet, nearer the Earth 
than any other, and having its orbit within the Earth's, 
is never seen far from the Sun. When she is in that 
part of her orbit where she rises before the Sun, she is 
called the Morning Star. The ancients supposed this 

Chapter XVI. — 1. What is related to show that the appear- 
ance of the Moon naturally awakes poetic ideas ? Of what 
class of poetic ideas is the extract from Burns, which you may 
repeat ? — 2. Of that from Milton, which may also be recited ? — 
3. Give an account of the appearance of the planet Venus, and 
of the opinion of the ancients concerning it. 



154 THE SUN AND MOON. 

to be different from the Evening Star, and called it " Lu- 
cifer, son of the morning.' ' When Venus is at that part 
of her orbit where she rises after the Sun, of course in- 
visibly, she is seen as soon as the withdrawal of his rays 
will permit. She remains above the Horizon for some 
time after his setting, and is then called the Evening 
Star. 

4. The diameter of the Moon is 2,160 miles, varying 
but little from that of the largest of the Asteroids. Forty- 
nine such bodies would be needed to make one of the 
bulk of the Earth ; — to make one the bulk of the Sun, 
more than fifty millions. In surface, there is not the same 
difference. The Moon-Observer would see the Earth as 
we see the Moon, except 13 times larger, and full, when to 
us the Moon is new. It would wax and wane through all 
the phases, from new to full, and the reverse ; and it would 
of course eclipse the Sun to the lunarians, as much more 
than the Moon does to us, as its surface is greater. 

5. The Moon's mean distance from the Earth is 
240,000 miles, while the Sun's is 95,000,000. Thus the 
Sun's distance exceeds the Moon's by nearly 400 times. 
But their apparent size is nearly equal, each showing 
upon the Celestial Sphere a mean diameter of a little 
more than half a degree. If bodies appeared less by 
distance, only in the direct ratio of the distance, the Sun 
would show immensely greater than the Moon ; but the 
ratio in which objects diminish to the view as they re- 
cede, is in the compound ratio of the square of the dis- 
tance ; that is, if a body is three times the distance of 
another, the bulk of the two being equal, their apparent 
sizes will be as 1 to 9 — since the square of 1 is one, and 
the square of 3 is nine. The apparent diameters of 
both the Sun and Moon are increased, when in or near 

4. What is the Moon's diameter ? How much smaller is the 
Moon than the Earth ? than the Sun ? What is the difference in 
surface of the Moon and Earth ? How would the Earth appear 
to an inhabitant of the Moon ? — 5. What is the mean distance 
of the Moon from the Earth ? of the Sun ? the comparative dis- 
tance ? What is their apparent size ? What is said of the ratio 
by which bodies appear less as they recede from the eye ? 






the moon's periodicity. 155 

the Horizon, by Kefraction. Their horizontal diameters, 
from the same cause, appear elongated. In certain states 
of the atmosphere, its powers of refraction are so in- 
creased, that the Sun and Moon sometimes appear on 
the edge of the Horizon to be about a degree in 
breadth. 

6. The Earth, as has been seen, has two motions — the 
Moon has three : one around the Earth, performed in 
about 27^ days ; one around the Sun, accompanying the 
Earth in her annual revolution ; and another around her 
own axis, on which she rotates once in 27^ days, the same 
time as her revolution round the Earth. By turning on 
her axis, she always keeps the same side towards the 
Earth. The fact that she does so, is known by observa- 
tion, and can be accounted for only on the supposition 
that she revolves on her axis in exactly the same time as 
she moves around the Earth. 

*?. The period of 27^ days is called a sidereal month, 
because it is the time of the Moon's passing from the 
meridian of any star until it return to the same meridian. 
But since the Earth is moving from west to east around 
the Sun, while the Moon is revolving around the Earth in 
the same direction — before the Moon, having set out from 
her conjunction with the Sun can come to the same point 
again, that is, to what is called the change of the Moon — 
she has to go on farther, to keep up with the Earth's 
course ; so that from change to change — that is, from 
new Moon to new Moon a^ain — is 29 d. 12 h. 44 m., 
which is called a synodic month. 

8. The Moon's orbit is an ellipse, having the Earth in 
one of the foci. The eccentricity of the Moon's orbit, or 
the distance of either of the foci from the centre, is cal- 

5. How are the apparent diameters of the Sun and Moon in- 
creased ? To what apparent size do they sometimes attain when 
on the Horizon ? — 6. What three motions has the Moon ? What 
is said of her revolution on her own axis ?-— 7. What is a sidereal 
month? What is the length of the synodical month? Why is 
it longer than the sidereal ? — 8. What is said of the Moon's 
orbit ? What is its eccentricity ? What is that of the Earth's 
orbit ? 



156 SELENOGRAPHY. 

culated at 13,333 miles. The Moon, when in its Perigee* 
or nearest station, must then be 26,666 miles nearer the 
Earth than when at its Apogee* or farthest station. The 
eccentricity of the Earth's orbit is 1,618,000 miles; so 
that when she is at her Perihelion* or nearest station to 
the Sun, she is 3,236,000 miles nearer than when in her 
farthest station, or Aphelion* 

9. Selenography, \ or Lunar Geography, has been of 
late studied by means of the immense telescopes which 
the elder Herschel, and others since him, have brought 
into use. It has thus been shown that those cloudy ap- 
pearances which children suppose to be the features of 
the "man in the Moon," are in reality deep valleys or 
the shadows of high mountains. Of these some have 
been discovered of the supposed height of nearly five 
miles. The principal are called by the names of cele- 
brated astronomers. Mount Newton is marked at 23,830 
feet. The elder Herschel discovered what he regarded 
as volcanoes in the Moon. 

10. From the variations in her place and appearance, 
at some times being nearer the Equator, and some times 
many degrees to the north or the south, and then changing 
in apparent size from a faint crescent to the full round 
Moon, it is no wonder that with the unlearned the Earth's 
satellite has little reputation for consistency and stabil- 
ity ; and that it should be said of capricious persons, 
that they are as changeful as the Moon. But in reality, 
though not in appearance, the Moon is as true to her ap- 

* These four words are derived from the Greek Helios is 
the Sun ; Gee, the Earth ; Peri, about or near ; Apo, from, re- 
ceding. 

f Selenography, from Selene, the Greek word for Moon. 

8. What is the difference between Aphelion and Apogee? be- 
tween Perihelion and Perigee ? How much nearer to the Sun 
is the Earth in her Perihelion than in her Aphelion ? How much 
nearer to the Earth is the Moon in her Perigee than in her Apo- 
gee? — 9. What is said of Selenography? How has the "man 
ip the Moon" been fairly put out of countenance ? What is said 
of lunar mountains? — 10. What is said of the changes in the 
Moon's place and appearance ? How is it in reality ? 



THE MOON 9 S CELESTIAL RANGE. 157 

pointed course as the Sun, The variations of the Moon's 
place in the Heavens may be understood by considering 
that the plane of the orbit in which she revolves around 
the Earth is nearly coincident with the common plane of 
the Earth's orbit and of the Ecliptic, making with it an 
angle of only about five degrees. The line of the inter- 
section of the plane of the Moon's orbit with this com- 
mon plane is called the Line of the Nodes, — the Nodes 
themselves being the points of the intersection of the 
Moon's orbit with this plane. The Moon, then, in her 
revolution around the Earth, is always either in the 
Ecliptic, or at most having only about five degrees of 
celestial latitude. Add this to the 23^°, the greatest 
declination of the Ecliptic, and it will give to the Moon 
a range of 28j° each side of the Equator, the double of 
which is 57° ; so that the Moon's place in the Heavens 
ranges in an Oblique Sphere from south to north, on the 
Meridian nearly one-third of a Great Circle of the Upper 
Heavens. There will be, as you may perceive by ex- 
amining the globes, a still greater number of degrees on 
the Horizon ; and this excess will be the greater, in pro- 
portion as the Observer's latitude increases."* The Moon 
moves around the Earth in the order of the signs from 
west to east. So also move all the other satellites of the 
Solar System around their primaries. 

11. Of all the laws by which the Almighty arranges 
and governs the material world, none which man has in- 
vestigated are so sublime as those of Gravitation. It is 
these, 

" "Which but to guess, a Newton made immortal." 

Gravitation is a term used to express that attraction which, 

* For a continuation of this subject, see the exercises following 
this chapter. 

10. What two planes make an angle of about five degrees ? 
What is the line of their intersection called ? What are the 
Nodes? What is the part of the Heavens where the Moon 
may appear — or, in other words, how far each side of the Equator 
can the Moon ever be seen ? In what direction does the Moon 
move around the Earth ? the other satellites around their prima- 
ries ? — 11. What is said of Gravitation ? What is its definition ? 

14 



158 LAW OF GRAVITATION. 

acting on all bodies, even the greatest, and at the remotest 
distances, binds the universe together. All solid bodies 
gravitate towards each other, — centre being attracted to 
centre, — and with a force varying in a ratio compounded 
of distance and quantity of matter. This ratio is the 
same as was mentioned concerning the effects of distance 
in diminishing the apparent size of bodies. If two bodies 
are equal, and at equal distances from a third body, they 
will gravitate towards it with equal force ; but if one of 
them has a distance compared with the other of 3 to 1, 
then the nearer — in a ratio of 9 to 1 ; that is, the quan- 
tity of matter being equal, in the inverse ratio of the 
square of the distance. But if the size of the farther 
body were trebled, as well as its distance, the gravitation 
of the farther body to the nearer would then be as 3 to 
9 ; that is, bodies gravitate towards each other directly as 
their quantities of matter, and inversely as the square of 
their distance. 

12. Hence, although the Sun is so much greater 
than the Earth, the Moon obeys the more intimate attrac- 
tion of nearness, and continues to revolve around her 
primary ; and hence the waters of the Earth are more 
attracted by the Moon than by the Sun. Solids, as we 
have said, gravitate in masses, centre to centre, but fluids 
not adhering together, every drop may be considered 
as a little separate globe gravitating by itself. The 
waters of the Earth, although held to its surface by a 
gravitation which impels each drop towards the Earth's 
centre, yet feel the attraction of the Sun and Moon- 
chiefly of the nearer influence of the Moon ; and as the 
centres of these bodies pass directly over the waters, 
the equilibrium of their attraction to the Earth is dis- 
turbed, and they rise up unequally. This rising of the 
waters of the Earth by the influence of the Moon and 
the Sun is called Tides. 

11. What is the ratio of the force of Gravitation? Give the 
example ? — 12. Give some examples in which the Gravitation of 
nearness prevails over that of superior quantity of matter. What 
difference is there in the manner in which solids and fluids grav- 
itate ? How is the equilibrium of the Earth's waters disturbed ? 
What are Tides? 



OCEAN TIDES. 159 

13. By the diurnal revolution of the Earth, parts of 
its ocean-surface are exposed to the direct action of the 
Sun and Moon. The particles of water are most at- 
tracted, and rise towards these points The crest-wave 
of the Tide follows the Moon (her attraction being the 
greatest) in her apparent daily course around the Earth. 
The inert matter of the waters does not, however, im- 
mediately follow the attraction, but about 36° in space, 
and 2h. 24m. in time, intervenes between the direct action 
of the Moon and the highest rise of the waters. On the 
side of the Earth, opposite to the crest-wave of the direct 
Tide, is another or opposite Tide ; while the parts of the 
Ocean 90° distant from these two highest points, have 
the waters most drawn from them, and they are conse- 
quently the lowest. In the places which the crest-wave 
is approaching, the waters are rising, and the Tide is said 
to flow ; while to those the crest-wave is leaving, the 
waters are lowering, and the Tide is said to ebb. 

14. When, by the Earth's diurnal rotation, the Sun 
and the Moon are either in conjunction — that is, in the 
same part of the Heavens, or in opposition — that is, in 
opposite parts of the Heavens — their united influence 
upon the waters, modified by the attraction of the Earth, 
causes the highest Tides. When they are in quadrature, 
or 90° apart, then the influence of the Sun raises the 
waters where that of the Moon depresses them, and there 
is then the lowest Tides. In the Moon's revolution about 
the Earth, she has one conjunction (when she is new), 
and one opposition (when she is full), and two quadratures 
(when she is said to quarter). At the Moon's opposition 
and conjunction, the daily Tides flowing the highest are 
then called Spring Tides. At the two quadratures they 
are at their lowest ebb, and they are then called Neap Tides. 



3 3. Give some account of their formation. What is said of 
the highest or crest-wave of the Tide ? What space and what. 
time intervenes between the Moon's direct action and the highest 
Tide? When do Tides flow? When do they ebb?— 14. When 
are Tides the highest ? When the lowest ? What are the highest 
Tides called ? What the lowest ? How many of each in a sy- 
nodic revolution of the Moon ? 



160 A NEW HYPOTHESIS. 

Fig. 24. 




Spring Tides 





Neap Tide* 



15. The ordinary explanation of the Opposite Tides is, 
that as the waters between the Moon and the Earth were 
drawn away from the Earth, so the Earth is in this case 
drawn away from the waters, which are farther than her 
centre from the Sun or Moon.* In whatever way the 

* The ordinary solution of the " Opposite Tides" to me ap- 
pears unsatisfactory. Whatever may be the cause, it is one 
which operates in regard to the Sun as well as the Moon, and in 
the same manner. Now, the Sun's distance from the Earth is to 
the semidiameter of the Earth as 24,000 to 1, and I cannot be- 
lieve that this minute difference will have any perceptible effect 
on the gravitation of the different parts of the Earth. Another 
solution of the problem has occurred to my mind, which I pro- 
pose to the learned for their consideration. To make the prob- 
lem more simple, let us leave the Moon out of the question, and 
regard the figure as if there were upon it only the Sun and the 
Earth. There will then be two forces operating upon the 
waters ; the gravitation which draws them to the centre of the 
Earth, and that by which they tend towards the Sun. That 
Which draws them to the Earth's centre is everywhere the 
greatest, or they would leave the Earth for the Sun. In the 
figure for the Spring Tides, take the point a. Here the forces of 

15. What three sources of gravitation are here mentioned, of 
which that of the Earth is the greatest ? Explain the causes of 
the direct Tide by the figure. 



OF OPPOSITE TIDES* 161 

Tides are explained, the fact of their existence is unde- 
niable, and also of their beneficial tendency, in thus keep- 
ing the whole mass of the waters of the sea in motion ; 
and so preventing their unwholesome stagnation. Navi- 
gation is also assisted by the Tides ; and the healthy salt 
water of the seas flows inland through the mouths of 
rivers. 

16. While we thus speak of the universal movement 
of the waters of the ocean by the Tides, we do not assert 
that any particles are made to travel great distances; but 
if some move, then those next must move to fill their 
places, those next to fill theirs, and so on. For the 
moving of such a myriad of particles, we can plainly see 
that some time is requisite, and that space is also needed 
for so vast an operation. Therefore, it is not strange that 
the Tides lag behind the Sun and Moon ; and that no in- 
land water, not even the Caspian Sea nor Lake Superior, 
has breadth sufficient lor the production of a Tide. 

17. Since the Moon's motion, producing a high tide at 
any place, produces likewise at the same time a high 
Tide at its antipodes, there will be two Tides for one day 

the Sun and Earth are directly opposing forces. They are 
opposing forces on the whole side of the Earth turned towards 
the Sun, but directly, only in that one point, and becoming less 
and less so as they recede from it. Of course the waters at that 
point have a greater portion of their gravitation towards the 
Earth balanced and destroyed by that of the Sun than those in 
any other place. That is, they are lighter, and the surrounding 
waters must pass under and raise them. But on the side of the 
Earth opposite the Sun, the two attractions will be, not oppo- 
site, but conspiring forces ; directly conspiring at b, and less so 
farther from that point. Of course at b the waters are heavier 
than at any other point on the Earth's surface ; and the sur- 
rounding lighter fluid will flow over and raise them, until an equi- 
librium is established. 

If this be the true solution of the Sun's opposite tides, it doubt- 
less is of those of the Moon, whose distance is to the Earth's 
semidiameter as 60 to 1. 

15. What is the ordinary explanation of the opposite Tide? 
What substitute has your author proposed ? (See note.) What 
beneficial tendencies have the Tides ? — 16. Is it supposed that 
any particles of water travel great distances ? 

14* 



162 the moon's, shadow, 

of the Moon; or, rather, for one completion of the 
Moon's daily circuit, which being in part a real motion 
in her orbit, added to the Earth's day, is 50 minutes 
longer. There is, therefore, 12 hours 25 minutes between 
each successive Tide. The difference in the height of 
Tides in different places varies from a few inches to 50, 
60, or even, as in the Bay of Fundy, to 70 feet. In this 
Bay, and in some others, the flow of the Tide is so rapid, 
that the horse and his rider are sometimes overtaken and 
destroyed. The average Spring Tide is to the Neap Tide 
as 7 to 3. 

18. The Moon's light is borrowed from the Sun. So 
is that on yonder wall ; his rays shine upon it through an 
open window, and are thence reflected to our eyes. We 
know this brightness on the wall to be nothing but the 
reflection of the Sun's light, because, if any opaque ob- 
ject is placed so as to intercept the rays, then the wall is 
so far dark, and the darkness or shadow takes the form of 
the intercepting object. By this would be known the 
opaque structure of the body casting the shadow on the 
wall — that of the wall itself, and also the figure of the 
intercepting object. When the Moon, being in opposition 
in her monthly revolution, comes into the Line of the 
Nodes, the Earth, then, directly between it and the Sun, 
casts upon it a shadow, which is always bounded by a 
circular line. No object but a globe will, in every direc- 
tion in which it can be placed, always cast a circular 
shadow. The Moon and the Earth are, therefore, opaque 
bodies, and the Earth is in figure a globe. 

19. When at her opposition the Moon is on or near 
the Node, then the shadow of the Earth, as shown by the 
figure, falls upon the Moon, and the Moon is eclipsed. 
When in conjunction the opaque Moon, in her monthly 
revolution, comes into the Line of the Nodes, then her 

11. In what duration of time will there be two Tides ? In 
what will there be one ? What is said of the height of Tides ? 
of the proportion between the Spring and the Neap Tides? — 18. 
From whence is the Moon's light derived & How is it known 
that both the Earth and the Moon are opaque bodieB, and that 
the Earth is in figure a globe ? — 19. When is the Moon eclipsed! 



SOLAR AND LUNAR ECLIPSES. 

Fiff. 25. 



163 




shadow falls upon the Earth, and to those Observers who 
are within this shadow (which, of course, is never large 
enough to cover the whole Earth), the Sun is eclipsed. 
(See figure.) The Earth being so much larger than the 
Moon, when her shadow falls direct, the Moon remains 
eclipsed for about two hours. The circular line is seen 
upon her disk, as she is going into the shadow and as she 
is coming out. Eclipses are partial when the Observer 
can see a part of the eclipsed body, total when the whole 
is obscured. An eclipse of the Sun is annular to an Ob- 
server who sees the Moon's shadow over the centre of the 
Sun with a luminous ring around it, which is a portion 
of the Sun's disk not obscured. 

20. Eclipses both of the Sun and Moon are calculated 
with unerring certainty for hundreds of years, either going 
backwards or forwards in time. This shows the con- 
stancy of the Creator's works, proving that the heavenly 
bodies move on, in exact time and place ; — and to be able 
to make such calculations, is a wonderful exhibition of 
what man can accomplish, when his investigations are 
pursued with educated powers of observation, imagination, 
and reasoning. But God is the Author of man. 

19. When is the Sun eclipsed? Can the whole Earth be at 
once in the shadow of the Moon ? What is sometimes the dura- 
tion of a Lunar Eclipse? When are Eclipses partial? total? 
annular ? — 20. What is said of the power of calculating Eclipses 
for long periods of time ? Are man's powers self-created ? 



164: ALLEGORICAL ILLUSTKATlOH* 

21. To illustrate these complicated operations of the 
Earth's satellite, let us again refer to our allegorical 
illustration of Mr. Teachwell and his inquiring boy, 
Charles ; now again descending the stairs by the summer- 
house, to embark on the little lake for a fresh voyage of 
observation round our lamp-sun.* To show how the Moon 
eclipsed the Sun, he placed between his own boat and the 
lamp a little boat with a sail ; and he made Charles ob- 
serve that while they were in the shadow of this sail, 
their Sun was eclipsed. When they were slowly passing 
out of the shadow, he made him remark how the line of 
the shadow passed gradually off, covering less and less of 
the luminous surface, as does the shadow of the Moon in 
eclipses of the Sun. 

22. Mr. Teachwell had a younger brother, a senior stu- 
dent in college, who was now spending his vacation at his 
brother's mansion. He entered into the father's views of 
encouraging the enthusiastic desire of his son to learn 
astronomy. Coming down the stairs at the moment, he 
offered his assistance. Mr. Teachwell at once accepted it, 
and said he wished him, since he was very alert, to get 
into the sail-boat, and play Moon. As such, it would be 
his duty to revolve about the Earth-boat (his own, with 
Charles for first Observer), while this primary planet-boat 
should sail in her orbit around the Sun. The young 
gentleman immediately sprang across the Earth-boat into 
that of the Moon. Both boats headed the same way, 
and, astronomically speaking, that was of course towards 
the East. Then, as the Earth moved on from her first 
position (a), where the Observer saw the lamp-sun in the 
constellation Statue, to the second position (6),f where 
that luminary appeared in the constellation Mansion. 
The nimble Moon-boat had nearly sailed from its point 

* See frontispiece. 

f The Moon-boat does not in this position appear on the fron- 
tispiece, but must be supplied by the imagination. It would 
have confused the picture. 

21. Eeferring to the frontispiece, how is an Eclipse of the Sun 
illustrated ? — 22. "What may here be illustrated concerning the 
Moon's motion ? 



CONJUNCTION AND OPPOSITION. 165 

of conjunction once around the Earth, and was again near 
to her point of conjunction with the island-Sun ; but it 
was clear that he must sail some farther, and occupy 
more time to come into conjunction than if the Earth- 
boat had stood still. 

23. When the Earth had arrived at the third position 
where the Sun was seen in the constellation Summer- 
house, the Moon (see frontispiece) had fallen a little back 
of the point of conjunction. In this station the Moon- 
boat is represented to be in opposition. Mr. Teachwell 
here stopped, and showed Charles how the Earth-boat 
had cast its eclipsing shadow on that of the Moon, and 
that the form of the shadow corresponded to that of the 
object intercepting the light. 

24. Mr. Teachwell then bade his son remark that the 
Moon-boat had moved in a series of loops about the 
Earth, because the Earth meanwhile had been moving too ; 
and thus was explained that the Moon was longer in 
going from conjunction to conjunction, because the Earth 
was moving around the Sun in the same way. Had the 
Earth-boat been moving in an opposite direction, she 
would have met it, and the time of her change would 
have been accelerated instead of retarded. Our collegian 
was so pleased with this mode of illustration, that he de- 
clared he would have a little round balloon made to re- 
present the Moon ; which he would fill with a light gas, 
and attach to his boat, and then they would make another 
joint revolution in such a style as would enable his nephew 
to understand the Phases of the Moon, which are her 
different appearances from new to full. Mr. Teachwell 
said the plan was perfectly practicable, and he asked 
Charles if he did not recollect that, when at the first posi- 
tion the sail was between them and the lamp, the sail 
looked black, because the side shone on by the lamp was 
turned away from them ; and he bade him observe that 
now, when the Moon-boat was in its opposition, the sail 



23. "What Eclipse is here illustrated ? — 24. What are Phases 
of the Moon ? What is the distinction between Phases and 
Eclipses ? 



166 the moon's phases. 

was bright, except where the shadow of their Earth-boat 
fell. 

25. There are Shadows to be considered in the cal- 
culation of Eclipses, but in the Moon's Phases there is 
only a difference of the Moon's position with respect to 
the Earth and Sun. Except when the Earth's shadow in- 
tervenes, the Sun always shines full on one half of the 
Moon ; but when the Moon is in conjunction, as at e {see 
Fig, 25), an Observer on the Earth has the dark side 
wholly turned towards him ; — then as the Moon moves 

Fig. 26. 




on towards her quadrature, at g, half her enlightened side 
— when through three-eighths of her orbit, at h, she is 
gibbous, and when in opposition, at a, her whole en- 
lightened side is seen, and she is in the full. Then she 

25. Describe the different Phases of the Moon, as represented 
in the figure ? 



THE MOON IN LONG NIGHTS. 167 

returns to her conjunction, where she will be again in- 
visible ; having waxed and waned by the same degrees, 
and through the same changes. 



EXERCISES. 

We wish our learners now to study the Moon's course in the 
Heavens, and endeavor, as fast as possible, to mingle science 
with pleasure as they gaze upon her silver radiance. Wherever 
the Moon appears, recollect that she is near the Ecliptic, never 
distant more than about 6° on either side, and always at least 
3° within the Zodiac; for the Zodiac reaches to 8° on each side 
of the Ecliptic. 

But the Moon, in her course around the Earth, appears to the 
Observer to pass during one revolution through every constella- 
tion of the Zodiac. To comprehend this, look again upon the 
frontispiece ; and suppose that the Earth-boat, with our observer, 
Charles, is at rest, and that the Moon-boat now carrying a light — 
for this must be evening — sails around it, slowly, so that Charles 
can have time to observe the circular line which the Moon's 
light makes as it passes over the objects — such as the Statue, the 
Mansion, <fcc. — which he has made the constellations of his little 
Zodiac. This lesser light of the Moon-boat will pass, as it re- 
volves once around the Earth-boat, over every one of the twelve. 
But the conjunction, when the Moon-boat comes to be in the 
same line, and is of course seen in the same constellation as the 
Sun, represents the new Moon. You must always then see the 
new Moon in that part of the Ecliptic where the Sun is ; or, 
rather, a little to the East, since just at the conjunction the Moon 
would set precisely with the Sun, and of course would not be 
visible. When you see the first thread-like crescent in the West, 
you must measure with your eye its distance from the Sun after 
its setting. If it is 13° * above the Sun's place, then one day has 
elapsed since the conjunction. If it is 26°, then the Moon is two 
days old ; and she has already advanced from the place of the 
Sun in the Ecliptic nearly or within 4° of a whole sign. Thus 
she goes on to her opposition at the rate of 13° a day ; and when 
she is in it, she rises large and bright and full, while the Sun is 
setting ; and of course if the Sun is then in Aries, the Moon is 
in Libra ; i. e. y in whatever constellation the Sun is, the Moon is 
in the opposite. 

From this we may learn whereabouts to look for the Moon's 
place at different seasons of the year. When the Sun is low in 
the South at the Winter Solstitial Point, that is where the Moon 

* In strictness, 13° 10' 86". 



168 THE HARVEST MOON. 

will be seen to set at the first appearance of her faint crescent ; 
but just as much to the North of East will she rise at her full ; 
for she is then opposite in the Summer Solstitial Point. The re- 
verse of this occurs when the Sun is in the Summer Solstitial. 
His amplitude is then towards the North, and the new Moon at 
her setting is by his side ; but in her opposition she is in the 
Winter Solstitial Point ; and she rises as much South of East as 
the Sun sets North of West. As the Sun nears the Equinoctial 
Points, this difference between the rising and setting of the Moon, 
as measured on the Horizon, diminishes, and when the Sun sets 
in Aries, the full Moon rises in Libra, and the reverse. 

Tins wise arrangement keeps the full Moon in oblique spheres, 
in that part of the Heavens where the Sun is not, and it also 
keeps the full Moon longer above the Horizon than the new; 
and this will be more and more the case as latitude increases : so 
that in the Frigid Zones the time of the Moon's appearance i9 
vastly greater than that of its occultation. 

The Harvest Moon is the name given to the Moon which fulls 
nearest the period of the Autumnal Equinox. It continues to 
rise nearly at the same time for several successive even- 
ings ; and as in certain regions of the Earth some of its fruits are 
about this time gathered in, it has been supposed an arrange- 
ment of Providence to aid in securing the harvest. But it is a 
necessary consequence of the varying inclination of the Ecliptic 
to the Horizon, by which, in Oblique Spheres, the smallest pos- 
sible angle between these two circles is made at this season of 
the year, as you may see by examining the Globe. So that the 
Moon makes her thirteen daily degrees more nearly parallel to 
the Horizon, and not so directly receding from it ; and thus she 
varies less from day to day in the time of her rising. 

On the Celestial Globe, complete the study of the Almacantar 
Zones. What part of the Earth's surface lies within the Fifth 
Belt or Zone ? What is its least distance from your own posi- 
tion at the Upper Vertex ? What is its greatest ? What part 
of the Earth's surface lies within the Sixth Zone ? Where are your 
Antipodes ? Of what Spherical System is that point the Lower 
Pole ? What is the Upper Pole ? The Great Circle. If any 
Secondary to this Great Circle should pass through these Poles, 
would its measure be that of the Earth's circumference ? 



CHAPTER XVII. 

The Sun's Effects upon the Earth. — The Oblique Sphere. — 
Earth's rate of Motion in her Orbit. — Gravitation. — Cen- 
trifugal Force. — Sun's Altitude, <fcc., at New York. — 
Triangle of Time. 

1. It is our object to put our learners in possession of 
principles, by which they can readily solve that great and 
multiform problem in Astronomical Geography, what is 
the Sun's appearance in every place on the Earth's sur- 
face, at every day in the year and every hour in the 
day ? One phase of this grand problem of the three 
Spheres* has been already noticed ; and two, viz., the 
Right and the Parallel Spheres, were partially discussed. 

2. The Oblique Sphere, it will be remembered, com- 
prises all the cases where, in the combined Spherical Sys- 
tems, the Axis of Movable Positions intersects, at an ob- 
lique angle, the Earth's Axis ; neither cutting it at right 
angles, as in the Right Sphere, or being parallel to it, as 
in the Parallel Sphere; and in every case of Oblique 
Spheres, the In tersections of the two Systems of the Earth 
and the Observer produce eight central angles, whereof 
four are angles of the Observer's Latitude, and the four 
alternates, angles of his co-latitude. 

* That the student need not be confused by similar terms with 
different meanings, we remind him, that the three Spheres here 
mentioned are different from the three Spherical Systems here- 
tofore denned and hereafter mentioned. 

Chapter XVII. — 1. What great problem is here noticed? 
What is one phase of the grand problem of the Sun's effects 
upon the Earth? — 2. Describe the Oblique Sphere, as to its 
difference from the other two, and the angles made by the 
Axis of the System of the Observer, with that of the System 
of the Earth. 

15 



170 EDUCATE THE HANB. 

3. The Oblique Sphere being the residence of all the 
inhabitants of the Earth, except the comparatively small 
number of those who live on the Equator, should be well 
considered, and will be best understood by examples. We 
will presently begin with the commercial capital of our 
country ; and we reproduce in the course of the chapter 
a former figure, because the Observer upon it is located in 
New York, and because all our former explanations of this 
diagram are now in point. 

4. But in order to acquire such clear ideas of this 
complicated subject as to retain them, we recommend to 
our learners, while on the subject of the Sun's appearance, 
to keep the Terrestrial Globe in view, with New York, or 
whatever place is under consideration, in the Upper Ver- 
tex ; and, besides, to make on the blackboard an enlarged 
copy of such parts of the illustrating figure as the sub- 
ject requires. And since there is plenty of room on the 
blackboard, — where your figure represents merely a Terres- 
trial Sphere, you can draw around it a concentric Celes- 
tial Sphere. In doing this, remember that although you 
may extend the Poles of your Terrestrial System to the 
Celestial and the planes of great circles, yet that another 
method must be pursued to obtain corresponding smaller 
circles. Straight lines diverging from the centre must 
here be used. Suppose you wish to obtain on the Celes- 
tial Circle, drawn on your blackboard, a line corresponding 
to the first Almacantar of your Observer, hold with one 
hand a string at the centre, and with the other carry it 
through one of the two intersections of the first Alma- 
cantar with the Earth's surface, and then extend it in a 
straight line to the inner surface of the Celestial Sphere, 
and dot the point of intersection ; then carry the string 
through the other extremity of the Terrestrial Almacan- 
tar, and find, in like manner its corresponding point on the 
Celestial Sphere. If you were drawing planes of circles 

3. What is the only exception to the fact that all the Earth's 
inhabitants live in an Oblique Sphere ? Why will the author re- 
produce in this chapter a former figure ? — 4. What does your 
author recommend as helps in getting clear ideas of this compli- 
cated subject? 



man's self-delusion. 171 

instead of figures representing the half of a convex sur- 
face of a Globe, you might revolve your string from one 
point to the other, and thus produce the true Almacantar 
Circle : — as it is, you must measure with your eye, and 
thus draw as best you may the circle between the two ex- 
terior points. 

5. Never lose sight of the distinction between Movable 
and Permanent Positions; nor ever allow any mere 
words, whether new or old, to stand in your mind for 
self-existent realities ; and thus make you forget that all 
the apparatus of the Observer (which you are in your 
drawings to represent by dotted lines), is nothing of it- 
self, but only a machinery which science-makers are obliged 
to invent, on account of man's finite and erring mind ; by 
which he is persuaded that he is at rest on the centre of 
the Earth, under the very dome-top of the Heavens ; when 
in reality the Earth he stands on is spinning like a top, 
and at the same time shooting like a meteor through the 
Heavens, at the rate of 68,000 miles in an hour and 
1,100 miles in a minute! It is enough to take one's 
breath away to think of it. But as our atmosphere 
moves with us, we are as quiet as is the infant who is 
carried in his mothers arms. 

6. When, however, you enter upon the threshold of 
the inner temple of the great science of Astronomy, for 
which it is our ambition to better fit our pupils than any 
preceding class have been, you will see how, in the ar- 
rangements of the Author of Nature, by this rapidity of 
motion, the safety of the Planets and the stability of 
their places in the Universe is insured. In the last chap- 
ter you were shown that gravitation is that grand in- 
fluence which binds the satellites to their primaries, and 
the primaries to the Sun. Perhaps some of you thought 
to ask, why, according to the laws of gravitation, do not 
the secondaries rush into the primaries, and the primaries 

5. What are you counselled not to lose sight of, and what 
must you not allow ? What is the Earth's rate of motion in her 
orbit ? — 6. What will the science of Astronomy teach you con- 
cerning the rapidity of the motions of the Planets I What ques- 
tion might a good scholar ask his teacher concerning Gravitation ? 



172 THE MOTION GIVEN TO THE PLANETS. 

into the Sun ? It would have been a sensible inquiry, 
and manifested you to be an accurate thinker. The full 
answer to this question we hope you will hereafter learn 
from the great astronomers, Kepler, Newton, and others. 
But thus much we now say, that the planets move in 
circular orbits around the Sun, by two forces, called 
the centripetal and centrifugal. The centripetal is that 
of gravitation, by which, on account of the superior 
weight of matter in a central body, the revolving one 
has such a tendency towards it, that it would go to it, but 
that the other force, the centrifugal, inclines it to fly off; 
not directly, for then the two would be merely opposing 
forces, and if they were equal, the body would not move 
at all, or if unequal, the body would move either directly 
towards, or directly from the central body — according to 
the direction given by the prevailing force. But the cen- 
trifugal force acts sidewise at right angles to the force of 
gravitation, and bodies moving between these forces 
are impelled by the centrifugal to go off from their orbits 
in tangent lines, but they do not, for they are held by 
gravitation to their central body. Thus the planets de- 
scribe, and with such inconceivable velocity, their per- 
petual circuits around the Sun, each in its appointed orbit. 
7. The centrifugal is also called the projectile force ; 
that is, the force by which the planets, in the beginning 
of their career, "when the morning stars sang together, 
and all the sons of God shouted for joy," were thrown 
forth by the power of the Almighty, in straight lines, and 
with a strength which, in the destined place of each, 
exactly balanced that of the gravitation to which it is sub- 
jected ; keeping, as it must, its destined rate of velocity, 
which, in the Earth, is, as we have said, 68,000 miles in 
an hour. 



6. What general answer may be given to this question ? What 
is said of the direction of the two forces ? What is the result ? 
{If any of the class are able, by previous study of the composition 
and resolution of forces, let them draw a figure and explain on 
the blackboard.) — 1. What other term is used to express the cen- 
trifugal force, and what does it mean ? When and by what was 
this force impressed ? 



THE TRAVELLER^ APPARATUS. 173 

8. Before resuming the subject of Oblique Spheres, 
we would remind our learners that the Sun's appear- 
ance and effects are changed by a change of place in 
the Observer, as well as by a change in the relative posi- 
tion of the Sun and Earth. Let us take for example the 
great traveller, Humboldt, who has seen the Sun rise and 
set in every possible sphere and position. He went from 
Alps to Andes, and from Andes to Himalaya, but remem- 
ber that as he went, he carried with him the whole appa- 
ratus of Movable Positions — the Observer's Line, the 
Zenith, Nadir, the two Horizons, the Vertical Circles, and 
the Almacantars. Had they been other than imaginary 
things, he would have needed an archangel's strength to 
move them ; but as it is, they only made him feel at home 
wherever he went. He would have been strangely miser- 
able had they not all appeared to be in their right places. 
Had he found some spot when he seemed standing on the 
verge of the Horizon, with the Zenith on one side, how 
would the world have appeared to him to be " out of 
frame !" But this never happens. . . When we have 
dwelt on these subjects until our imaginations conform to 
reality, we shall have gained a great point in Astronomical 
Geography. 

9. In Figure 27, which is wholly terrestrial, the Upper 
Vertex is at New York, in N. Lat. 40° 42 '. Our Ob- 
server on the diagram may, for aught we know, have 
been Hendrick Hudson himself, looking abroad upon the 
goodly domain which he had just discovered. Whoever 
he may be, the dotted lines express positions which will, 
when he moves, move with him. But the same will also 
exist for the remaining; Observers at New York. Terres- 
trial vertical circles descend in every direction from the 
Observer's place, and intersect at right angles a circle 
which is everywhere 90° from it, and which is of course 
his Horizon. The Vertical Circle, whose profile is here a 
straight line, is the Observer's Prime Vertical, since it 

8. By what is the Sun's appearance and effects changed ? What 
example is given of a traveller who has seen the Sun's rising and 
setting in all possible positions ? and what would make him feel 
at home in all ? 

15* 



r74 THE PERMANENT AND THE MOVABLE. 



Fig. 2T. 



NEW YORK 




MAY 107 ; 

sun's UST. dec .18° : 12.420 



6.210 



crosses at right angles the North and South Vertical ; 
which of course that is, in which the North and South 
Poles of the Earth are found. Observe that the outer 
circle of the diagram is composed of two, the one in a 
dotted, and the other in a firm line. It is thus made, 
because here are two coincident circles, the one an 
hour circle, belonging to the Permanent, and the other — 
namely, the Observer's Meridian — identical with his North 
and South Vertical, belonging to the Movable Positions. 
Between each of these two principal Verticals are drawn 
two others. The ^.ve Almacantar Circles, of which the 
Horizon is the third, are here set down, with the easily- 
remembered numbers ; by which our dignified little Ob- 
server looks as if " he stood and measured the Earth." 

10. All these imaginary circles, it must be remembered, 
may be transferred from the Earth to the Heavens, or 



9. Draw and describe the figure as respects a New Ycrk Ob- 
server. 



LONGEST ASTD SHORTEST DATS. 175 

they may have been transferred from the Heavens to the 
Earth— the Great Circles, by means of imagined planes 
which cut both spheres alike ; and the small circles, by 
imagined straight lines going to and coming from the 
centre of the Earth to the Celestial Sphere. 

11. Let us now, with our Globe and diagram before us, 
proceed to consider how we shall find the altitude of the 
Sun and the length of the day in New York at different 
times of the year. Such observations are often made at 
noon. What, then, we will first inquire, is the Sun's ap- 
pearance at New York at the Summer Solstice ? To find 
his Meridian Altitude on the 21st of June, we may add 
23° 28', his northern declination on that day, to 49° 12', 
the complement of the Observer's latitude. The Sun's 
altitude at New York will then be found on the 21st of 
June to be 12° 40', and his Zenith distance 17° 20'. This 
will be the same in every place on the Earth of the same 
latitude. The 21st of June is the longest day in the 
year, not only to the people of New York, but to all per- 
sons in North Latitude ; and it is the shortest to all per- 
sons in South Latitude. Examine the Globe, and learn 
what will this day at New York be the Sun's Amplitude. 
The Sun's circle of motion for this day describes, as he 
passes through the Heavens, the Tropic of Cancer. The 
number of degrees north of the points east and west in 
which this circle cuts the Horizon, shows where he rises 
and sets, and are, by definition, his Amplitude for this 
day. 

12. What is the Sun's appearance at New York at the 
Winter Solstice ? To find his Meridian Altitude for the 
21st of December, we must subtract his declination (which 
is 23° 28' south) from the Observer's co-latitude. To 
find the Sun's Zenith Distance, we may subtract his Me- 
ridian Altitude from 90°, that of the Observer's Zenith. 

13. There are various methods of finding the length of 

10. How may these imaginary lines be transferred ? — 11. "What 
will be the Sun's altitude, &e., at ]S T ew York on the day of the 
Summer Solstice ? At what time are the days in the northern 
hemisphere the longest ? — 12. Where will the Sun appear to the 
Observer at ]S"ew York on the day of the Winter Solstice ? 



176 TRIANGLE OF TIME. 

the Observer's day from the Globe, but they are all pred- 
icated on the principle that his place being made the 
Upper Vertex, the diurnal arc of the Sun's circle of mo- 
tion far the given day will contain so many times 15° as 
the day sought contains hours^ and the odd degrees are to 
be reckoned four far a minute* To find these out, use 
your own method ; but in these problems respecting time, 
we do not recommend much attention to the index hour- 
circle, as it sets the learner to turning the Globe, which 
puts the Observer out of his only true place, as having 
the Horizon 90° from him. Generally speaking, keep 
your Observer in his Upper Vertex, and consider that it 
is for him that you are to find the length of the day ; but 
remember, that if you find the length of the day for the 
Observers of a certain place, you find it for all others in 
the same latitude. If, therefore, we can discover a gen- 
eral easy method of finding the length of the day for the 
latitude of our Observer, we shall thus find it for him and 
all others at the same distance from the Equator. 

14. To give such a method, and for other reasons — this, 
however, being the principal — we will introduce our learn- 
ers to a certain triangle on the Globe, which, for short- 
ness, we will call the Triangle of Time, as it might, with 
propriety, be called the Triangle of Declination, Ampli- 
tude, and Time. The Latitude of the Observer and the 
time, or what is equivalent, the Sun's declination, must be 
given. We are considering, then, the Sun's appearance 
to the Observer at New York. We wish to find the 
length of his longest day, the Sun being then in the 
Tropic of Cancer. But we shall find it for him if we find 
it for his Latitude, for which the North Pole is now ele- 
vated. We will then revolve the Globe on its axis until 
we bring one of the Colures (vi o'clock hour-circles) 
under the Meridian. Let it be the Solstitial Colure. 

13. On what are the various methods of finding the length of 
the Observer's day predicated ? If you find the length of the 
day for the latitude of your Observer, for whom else will it be 
found? — 14. What Triangle in name and quality does your author 
here introduce ? How is such a Triangle constructed for finding 
the length of the longest day in New York ? 



MULTTJM IN PARVO. 11 / 

15. Then the Triangle of Time will be formed both in 
the east and in the west (towards the elevated Pole) by 
the intersection of three circles — 1st, the Equinoctial Co- 
lure ; 2d, the Horizon ; and 3d, the Sun's circle of daily- 
motion for the given day, the 21st of June, the circle 
being then coincident with the northern Tropic. Examine 
this Triangle on the Globe. The side which we call the 
first is the intercepted arc of the Equinoctial Colure, and 
being a secondary of the Equator, it is the measure of 
the Sun's declination, which this day is 23° 28'. The 
side which we call the second is the intercepted arc of the 
Horizon, which, by definition, is the arc of the Sun's Am- 
plitude for the Time and Latitude. The third side is the 
intercepted arc of the Surfs circle of motion for the given 
place and day. 

16. This third side is a portion of the Observer's Diur- 
nal Arc ; and (reckoning from the Meridian downwards 
on either side) it is what remains after taking out 90°, or 
its equivalent, six hours. Reckon the degrees of this 
third side in time — double the amount, because there are 
two triangles, and add the double to 12 — the number of 
hours of the 180° between the east and west sides of the 
Equinoctial Colure : — and you have the length of the 
given day. For the latitude of New York, we find the 
third side of the triangle to be about 37-|°, or 2 J 
hours, the double of which, added to 12, would show 
the longest day at New York to be about 15 hours. 
Of course, the shortest night must be on the 21st of 
June, also ; and 9 hours — since that is what remains of 24 
hours, 15 being deducted. If we take the same latitude 
south, the same day will be 9 hours and the night 15. 

17. This Triangle of Time belongs to the Oblique 
Sphere within the Polar Circles. Rectify the Globe for 

15. Describe from the Globe the first side of this Triangle? 
the second? the third and principal? — 16. Explain the manner 
in which the third side of the Triangle is to be used, to find out 
the length of the day in any given latitude at a given time or 
declination ? Give the time of the longest day for the latitude 
of New York? What will, on the 21st of June, be the length 
of the day and night in the same latitude south ? 



178 AMPLITUDE EXCEEDS DECLINATION : 

the Observer on the Equator, and the vi o'clock hour- 
circle, or Colure, coincides with the Horizon, and every 
diurnal equals every nocturnal part of each circle of daily 
motion ; and although the Meridian Sun from the 20th of 
March to the 21st of June is going farther and farther 
north, and from that time to the 23d of September is 
coming back, and is on that day Vertical — then going south 
to the 21st of September, and then returning, still every 
day is of the same length — twelve hours day and twelve 
hours night, and the Sun descending direct below the 
Horizon is soon beyond the reach of affording even a faint 
Twilight. 

18. But as soon as we take an Observer away from the 
Equator, and put his place in the Upper Vertex, this 
triangle is formed on the Globe ; and since to understand 
it well, is to be able to answer at once many of the most 
common problems to be performed on the Globe, we will 
pursue the subject some farther. Remember that the 
latitude of the Observer must be given, and the Globe 
rectified accordingly ; — that the declination of the Sun 
must be given, or the day of the month by which it may 
be found. Then, of course, we know the circle of the 
Sun's motion that day. Observe how this triangle will 
alter as the Observer's latitude is changed. We will still 
leave the Sun's declination to be 23|°, and now give the 
problem to find the length of the longest day in that 
latitude. Observe the effect of the convexity of the Earth 
on the different sides of the triangle. Declination is 
23^°, while Amplitude has increased to 30°. And the 
third side shows 15°, or its equivalent, one hour. This, 
doubled and added to 12, is 14 hours, the length of the 
day on the 21st of June, the longest day in that latitude. 

19. Next, let our Observer's latitude be 49°. The 
triangle shall keep its first side, that of the declination, 
the same, the Sun's extreme northern limit, 23^° — the 

17. To what Sphere does this Triangle belong? What is the 
position in this respect of the Observer on the Equator? — 18. 
Take some place in Latitude 30°, and by the Triangle find what 
will be the Sun's Amplitude and the length of the day on the 
21st of June, or of the longest day in the year. 



CEASES AT THE POLAR CIRCLES. 179 

second side showing the Sun's amplitude in this declina- 
tion and in 49° N. Lat, gives us about 40°, and the third 
side gives us 30°, or 2 hours, which, doubled and added 
to 12, makes 16 hours, the length of the longest day in 
Latitude 49°. 

20. Keeping still the extreme northern declination of 
the Sun, that the learner may comprehend how, the Sun 
remaining stationary, the change of place in the Obser- 
ver varies the great problem of the Sun's appearance, we 
will now suppose our Observer in N. Lat. 66^°, the ex- 
treme latitude where the Globe, elevated to the Observer's 
place, will form our useful triangle. And now what sur- 
prising effects do we see from the convexity of the Globe ! 
While the first side remains the same, the two other have 
now increased to 90°. The Sun rises where it sets, and 
sets where it rises, due north. Here is day without 
night. If we take a latitude still higher, we shall be 
within the region where there are days* in midsummer 
when the Sun never sets, and in midwinter when he never 
rises ; and these days will increase in number as we go 
towards the Poles. 



EXERCISES. 

Accustom yourselves, in looking at the Heavens, to reckon by 
hours as well as degrees, In learning the Stars, be sure to 
strengthen your impressions concerning the locations of the 
Colures. If you have not already done so, mark and remember 
the bright star Alpherat, in Andromeda. It is in the Vernal 
Colure, about 30° south of Caph. And this Colure forms the 
initial line from which both Right Ascension and Time begin. 
"When it is the Zero of time (that is, midnight) under the Vernal 
Colure, it is vi in the morning under the Summer Colure, xn 
at noon under the Autumnal, and ti in the evening under the Co- 
lure of the Winter. Or suppose it m in the morning at the 

* That is, using the term day to mean 24 hours, or one diurnal rotation. 

19. What in Latitude 49° do you find by the Triangle is your 
Observer's longest day, or, which is the same, the length of his 
day on the 21st of June ?— 20. Why is the Latitude 66£° given 
in the next example ? What do you find in this latitude con- 
cerning Amplitude and Time? Suppose the Observer goes be- 
vond this latitude into the Frigid Zone ? 



180 ASTRONOMY AS EXPLAINING GEOGRAPHY. 

Vernal, then at the Summer it will be ix, a. m., at the Autumnal 
in, p. m., and at the Winter ix. Consider this in connection with 
Right Ascension, and you will find 15° are taken for each hour 
of the 24 when reckoned from the initial or Zero point. At mid- 
night, on the Vernal Colure, are hours and 0° ; at the Summer 
Colure vi hours and 90° ; at the Autumnal, xn hours and 180° ; 
and at the Winter, 18 hours and 270°; and the six hours till 
midnight take it the 24 hours which complete the circle of time, 
and the 360° which accomplish that of the corresponding space. 

It is our object so to explain the Globes that ail the problems 
belonging to Astronomical Geography can be easily solved by 
them. We do not profess to treat of pure Astronomy; and 
therefore those problems in the books which have heretofore been 
written respecting the Globes, and which refer solely to Astron- 
omy, we leave for our pupils to solve, after they shall have be- 
come more fully acquainted with that noble science. 

When the author of this work was in Europe, an American, 
who had long resided in Paris, said to her, " Why cannot our 
young countrymen be persuaded to learn their own country be- 
fore they come here ?" So might the stars if they had voices say to 
many a young student of Astronomy : Why do you not learn 
the Earth, before you attempt to understand the Heavens ? 

But the Earth is herself a star in the Heavens ; and to under- 
stand terrestrial appearances — to know especially how the Sun 
affects the Earth, considering her motions annual and diurnal, 
and the convexity of her form — it is necessary to go a certain 
distance into Astronomy. But questions which have no relation 
to the Earth, we do not undertake to explain. 

We have said little in our Exercises concerning the use of the 
index of the hour-circle, because we have, in the course of our 
experience in teaching, found pupils who had become expert in 
its use, and in solving problems connected with it, who did not 
understand the principles on which they proceeded. But we 
trust that those who have faithfully followed our instructions 
can now answer all the questions which can be made out of 
these problems, so far as Astronomical Geography is concerned, 
either with the use of the index or without it. The upper 
brazen Meridian in many cases answers the same purpose as the 
index. For an example, take New Orleans. Bring it under the 
brazen Meridian. The hour vi is under the Meridian, also. If 
you turn the Globe either way, 4 hours to x east, or to n west, 
you will have turned it 60°. The hours east will be earlier, and 
those west later, and all places under the same Meridian have 
the same hours. 

Suppose it now to be six o'clock in the morning at New Or- 
leans. You wish to know what will be the hour at any other 
place or places. First let it be Halifax. Turn the Globe the 
way that will soonest bring Halifax to the Meridian, and then 
observe the hour on the circle. You find it about vn and 45 



LATITUDE SUGGESTIVE. 181 

minutes, which is of course later in the day, it being east Next 
we ask concerning the time at San Francisco, it being vi in the 
morning at Xew Orleans. We find it about 8 minutes after iv. 
It must of course be earlier than the time at ]S~ew Orleans, since 
the place is west. How many degrees of longitude are these 
two places from New Orleans? Halifax is ljh. X 15°, which 
is equal to 26^°. San Francisco, multiplying in the same man- 
ner the hours by the degrees, is 32° from New Orleans. In the 
same way bring the place to the Meridian, and set the index to 
the hour, and turn the Globe, and the index, when the place 
sought comes under the Meridian, will point out the hour. But 
knowing the longitude, you can always readily change it into 
time. And it amounts to precisely the same thing if you count 
the hour-circles as so many hours. For example, place your fin- 
ger on Philadelphia, which is on an hour-circle.* What places 
will have all their hours the same ? Those on the same hour- 
circle. What will have all their hours one hour later than Phila- 
delphia ? All those which are under the hour-circle next east. 
Those under the hour-circle next west will have all their hours 
one hour later, and so on till you come to the inferior Meridian, 
where it is noon when at Philadelphia it is midnight ; there being 
180° and 12 hours difference. 



CHAPTER XVIII. 



Causes of the difference in the Length of the Days and 
jSTights. — Effects and Appearance of the Sun. — The Obser- 
ver at ]Sew York on the 10th of May. — What the Length 
^ of his Day, &c. — Observer at Buenos Ayres ; at Stock- 

holm ; at Cape Horn ; at Quito ; at the JSorth Pole. 

1. We should become so thoroughly familiar with the 
grand problem of the Sun's terrestrial appearance, that 
when we read in any book of travels or geography that 
such or such is the latitude north or south of any place, 
we shall at once raise our thoughts to the Heavens 

* Strictly speaking, 15° 11" from Greenwich. 

Chapter XVIII.-— 1. What information is it desirable that 
latitude should afford ? 

16 



182 INCREASE AND DIMINUTION. 

from thence, and in fancy behold the Sim ; — if in or near 
the Equinoctial, rising in the east, mounting upwards 
towards the Zenith, and setting in the west ; — or else- 
where, at noon bending either to the north or south 
according to the latitude, and setting with a larger or 
smaller amplitude. Patient investigation is the mother 
of accurate knowledge ; and we must not too soon tire of 
important subjects. 

2. Let us remember that there are two causes of differ- 
ence in the length of the days and nights. The first is the 
difference of the place of the Observer on the Earth's sur- 
face. We now understand that if the Sun held exactly 
the same position, — and that position not in the Equinoc- 
tial, the length of the Observer's longest day would wholly 
depend on, and vary, with his own place, as it approached 
or receded from the Equator, since in receding he carries 
his Horizon along with him, which, according to his lati- 
tude, intersects differently both the Equator and the 
Ecliptic. 

3. But, secondly, the days, except at the Equator, vary 
in length also, as we have seen in the chapter on the sea- 
sons, by the Earth's annual motion around the Sun with 
an axis oblique to the plane of the Ecliptic. Thus the 
stationary Observer, not on the Equator, experiences a 
constant transition in regard to the length of his days ; — 
slow when he is near the Equator, and becoming more 
and more rapid as he approaches the Polar Circles ; the 
length of the days diminishing from the summer to the 
winter solstice, and increasing in the reverse order from 
the winter solstice to the summer. So that every such 
Observer has two days in the year of the same length, 
with the exception of the longest and shortest days, which 
come but once a year : and as a general rule, with excep- 
tions hereafter noticed, the two equal days will be those 
equally remote from the longest and shortest. Should 

2. What are the causes of the difference in the length of the 
days and nights? What is it presumed that the learner now 
understands ? — 3. What does the stationary Observer without 
the Tropics experience ? What is said of certain equal days ? 
of nights in one latitude equal to days in the other ? 



ALTITUDE AND ZENITH DISTANCE. 183 

you desire to find the length of the day in any south 
latitude, it would answer the same purpose to find 
the length of the night, in the corresponding latitude 
north. 

4. For the purpose of showing how (the Observer re- 
maining stationary) the Sun's appearance changes with 
the time of the year, we will next inquire where, at the 
10th of May, and in the latitude of New York, is the 
Sun's circle of daily motion. On the Analemma we shall 
find that the Sun's Declination on the 10th of May is 19° 
north ; and the parallel of latitude passing through this 
point, will therefore be the terrestrial line where the Sun's 
vertical rays pass over the Earth on this day. "What, 
then, will be the Sun's Zenith distance to the Observer at 
New York on the 10th of May? Since his Declination 
is north, his Zenith Distance will be the latitude of New 
York, minus his Declination ; that is, 40° 42 ' — 19° = 
21° 42'. . . What at this time and place will be the Sun's 
Altitude ? From the Zenith to the Southern Horizon 
being 90°, subtract from this, 21° 42 ', the Zenith Dis- 
tance, and 68° 18' is found to be his Altitude. 

5. For the length of the day in New York, May 
10th, observe our Triangle of Time, of which the third 
side will, on this day, be the parallel of North Latitude 
1 9°, instead of the Tropic of Cancer. Of this parallel we 
find, by examining the Globe, there is intercepted between 
the Horizon and the vi o'clock hour-circle about 21°, 
which is nearly equivalent to 1 hour and \ in time. Twice 
\\ added to 12 makes 14 hours and a half, which is 
therefore the length of the day at New York, and all 
other places of the same latitude, on the 10th of May. 
How many degrees from the point east and west will the 
Sun at New York, on the 10th of May, rise and set? 
This is inquiring what is the Sun's Amplitude ; and our 
convenient triangle will show, by the intercepted arc of 
the Horizon, that it is about 28°. Nature, with us in 

4. How may the Sun's Altitude and Z. D. at New York on the 
10th of May be determined ?— 5. How on the Triangle of Time 
can you find the length of the day at New York on the 10th of 
May * And what is the Sun's Amplitude ? 



184 



SOUTH LATITUDE. 



New York, is now smiling in the loveliness of spring, and 
rejoicing in the prospect of approaching summer. 

6. Now, let us vary our grand problem by removing 
our Observer to the South of the Equator. Let his place 
be Buenos Ayres, 34° 36' S. Lat., and the time the 10th 
of May. To this Observer, as to us, the topmost point 

Fig. 28. 

BUENOS AYRES § UT> 




twiayIO i sun'sN. dec.19° 



of the Heavens appears to be precisely over his own 
head. On the 20th of March, when we had our Vernal 
Equinox, he had his Autumnal, and when we saw the 
Equatorial line which the Sun described on that day 
bending to the South, he saw the same line in the Heav- 
ens bending to the North. Still farther is it now rece- 
ding towards the North, for to our present Observer the 
Winter Solstice, the 22d of June, is approaching, and 
vegetation has already felt the withering power of frost. 
7. The Sun's Zenith Distance must here be found by 

6. Where are you next to locate the Observer ? Taking the 
same time as at New York, what contrasts are observable ? 



OtTR ANT(ECl. 185 

adding his declination (19° north) to the latitude, and his 
altitude, by subtracting the Zenith Distance from 90°. For 
the length of the day when the Sun's declination is 
towards the depressed Pole, we cannot conveniently ex- 
amine our triangle, because it is below the Horizon ; but 
we can, for the occasion, change the declination to 19° 
south, and then for the length of the days as shown by 
the intercepted arc of daily motion — that is, of the Diur- 
nal, which we thus make the Nocturnal Arc — we shall get 
the length of the nights, and subtracting that from 24, we 
shall have the length of the day, which, when the decli- 
nation is towards the Pole, is of course always less than 
12 hours. 

8. Thus, people of opposite latitudes have opposite 
seasons. Those whose latitudes are equal as well as op- 
posite, and whose meridian is the same, are called 
Antoeci. Thus, the people of Valdivia, in Chili, are the 
antceci of those of New York. Their hours of the day 
are the same. They have noon and midnight at the same 
moment ; but while in November we are suffering all the 
discomforts of approaching winter, the Valdivians are en- 
joying the soft green of the fields and the bloom of the 
opening flowers. 

9. We will now give our learners two other diagrams 
- — one of an Observer at Stockholm, in a high Northern 
Latitude, and the other at Cape Horn, in a high Southern 
Latitude. We leave them to draw these figures at large 
on their blackboards, to rectify the globe at the same time 
for the Observer at each place, as the two are successively 
taken under consideration ; — then 'to learn from the Tri- 
angle the Sun's amplitude and the length of the days 

?. How is the Sun's Zenith Distance to be here found ? Why 
can we not in this case, as in that of isew York on the 10th of 
May, examine our Triangle of Time ? But, for the occasion, what 
will answer the same purpose ?— 8. What persons have opposite 
seasons? When on the same Meridian, what are they called? 
What is said of the people of Valdivia, in Chili ? — 9. Draw a 
figure representing an Observer in Stockholm ; and in contrast 
draw another, representing one at Cape Horn. The latitude is 
given, and the time being the 21st of June, what is the length of 
the day in each? 

16* 



186 



POSITIONS CONTRASTED, 



Fig. 29. 




JUNE 21 SUMMER SOLSTICE 



JUNE21 WINTER SOLSTICE 



and nights ; and, in short, to answer, concerning these 
places, the same questions respecting the Sun's position 
and effects, in regard to climate and seasons, as have been 
considered and replied to, in the cases of the Observers 
located at New York and Buenos Ayres. — Thus far we 
have treated of Oblique Spheres. 

10. In order briefly to review the subject of the Right 
Sphere, suppose we fancy ourselves to be Observers at 
Quito, on the Equator, at the 20th of March. We are 
on the declivity of the sublime Andes ; but even although 
the Sun is vertical to our position, still our climate is as a 
perpetual spring. Being 9,500 feet above the level of the 
sea, we experience the coolness of the upper regions ; and, 
besides, the sloping mountain receives not directly but 
obliquely the rays of the Sun. We see him rise in 
the east, mount directly upwards to our Zenith, and 
descend directly to the west. But he is passing onwards 
to the north. Every day he will describe a circle a little 
north of that of the preceding day, until, on the 21st of 
June, he will rise with an amplitude equal to his declina- 
tion 23^°, and describing his whole daily course thus far 
to the north, set with the same. 

1 1 . The globe will not now show for our position any 

9. What is to each the Sim's Altitude and Zenith Distance ? 
What his Amplitude ? — 10. Reviewing the Right Sphere, what, 
if we fancv ourselves Observers at Quito, shall we observe? 



LIV1KG ON THE EQUATOR. 187 

Triangle of Time. The third side has disappeared, for 
the two first now coincide. Nowhere else, except at the 
Equator, is this the case. But although the Sun goes 
thus far north, returns, and in six months is just as far 
south, — still every circle of his daily motion has to us its 
nocturnal, equal to its diurnal arc, and our days and 
nights are invariably 12 hours each in length. But 
our seasons seem strangely confused. Our nearest ap- 
proach to winter occurs twice a year at both the Solstices, 
and our two summers are when the Sun is vertical ; our 
two autumns are when he is going from us, and our two 
springs when he is approaching ; and we have the glo- 
rious privilege of seeing, in the course of the year, every 
star that decks the firmament, as each, save Cynosura, in 
the northern Horizon, performs in its season, its quarter 
of a circle or 6 hours direct from the Horizon up to the 
Meridian, and direct!)' down again in the same 6 hours' 
time. The Moon, as usual when she is new and young, 
is in the west, close by the side of her lord, the Sun ; but 
when she comes to maturity, she shows him her full 
face in direct opposition, both as respects the Horizon and 
the Ecliptic. Her amplitude to an Observer on the Equa- 
tor will, in her opposition, be therefore south, when the 
Sun's is north, and the reverse. 

12. Concerning Parallel Spheres, although we are not 
aware that any human being has yet seen the Sun from 
either of the Poles, yet travellers have approached them 
within eight degrees ; and the principles on which we 
reason are so thoroughly established, that we know for 
certainty how the Sun would appear ; and to dwell there 
for a time, though but in fancy, gives to the mind a feel- 
ing of strange sublimity. We will suppose ourselves at 
the North Pole, and that it is the beginning of the Astro- 
nomical year — the noon of the Vernal Equinox. We 

11. In a Right Sphere, how is it respecting the Triangle of 
Time ? Have the inhabitants at the Equator four seasons only 
like those of Oblique Spheres? What is said of the Moon? — 12. 
Concerning the Parallel Sphere, have we knowledge that the 
Sun has been seen from either of the Poles? Do we know 
what would be its appearance ? 



188 A DWELLER AT THE K. POLE. 

shall then, as dwellers of a Parallel Sphere, have lived 
six months without seeing the Sun. The northern Polar 
Star has shone brightly from our Zenith, and all the stars 
of the northern constellations have moved around it, each 
describing its perpetual Almacantar Circle once in 24 
hours. The Moon meantime has been our friend, having 
been below the Horizon with the Sun only when she was 
new ; but as she approached maturity, she began to wind 
her spiral up our sky — reached her maximum altitude of 
28^-° at the full, and then descending as she rose, she was 
absent a few days from our view, shortly to appear again, 
and with her brightness renewed, to trace her monthly 
windings up and down our sky. The Twilight, too, shone 
as long as the Sun was within 18° of our Horizon, and 
thus cheered all, except iive weeks, of our dreary night of 
six months. Then the Aurora Borealis gladdened us by 
its most beautiful coruscations, sometimes gorgeous with 
all the colors of the rainbow, and sometimes dazzling us 
with flashing streamers of uncolored light. As the glo- 
rious Sun approached, the Twilight increased in brightness, 
until it became the full radiance of morning. How did 
we rejoice when his first rays broke forth ! Now at the 
noon of the Vernal Equinox, half his disk — intersected by 
the Southern Meridian — is above our Horizon. 

13. The Earth turning on her axis in the order of the 
signs, is revolving towards the East ; and the Sun — his 
circle of motion to»day being the coincident Equator- 
Horizon — is apparently moving in the contrary direction 
from South towards the West, and is found in that point 
of the compass at the evening vi o'clock. He still moves 
in the Horizon, and is at the North at the midnight xn, 
in the East at the morning vi, and at the noon xn, again 
in the South. We find as he comes to the Meridian on 
the succeeding days that he has risen about a quarter of 
a degree. And so for three months, or about 91 days, he 

12. If we were actually there at the beginning of the Astro- 
nomical year, what would have been the state of things for the 
months previous? — 13. Describe the Sun's appearance for the 
six months during which he is in a Parallel Sphere above the 
Horizon. 



ANNUAL WITHOUT DIUENAL MOTION. 189 

keeps circling round and round in his spiral motion, 
rising a little higher and a little higher every day ; until 
at length, on the 21st of June, he comes to his upper 
declination of 23^°. There he seems to be stationary for 
a few days as he performs his diurnal circuits, and then 
he winds and wheels down and down by little and 
little, until at length, at the end of another three months, 
he is on our Autumnal Horizon — soon to descend and 
visit with his cheering rays the Southern Pole ; while 
again he leaves the Northern to six long months of cold 
and darkness. 



EXERCISES. 

Suppose that at midnight the moment of commencing the 
Astronomical Year the Earth should stop rotating on her axis 
for just one year, what appearances would the Sun and heavenly 
bodies present ? This is an important problem, for when com- 
plicated things are to be understood in connection, it is of great 
use to understand each single thing by itself. The appearances 
of the heavenly bodies are complicated, and result from the com- 
bination of three distinct things. First and much the most 
striking is that of the Earth's diurnal motion, by means of which 
all appear each day to revolve round the Earth ; second, the 
Earth's annual revolution, by which the Sun appears to move 
round the Earth once a year ; and, third, the proper motion of 
the heavenly bodies belonging to the Solar System, especially 
that of the Earth's own satellite, the Moon. 

The apparent daily motion of the heavenly bodies does not 
confuse and trouble the young learner so much as the apparent 
annual motion of the Sun. Moving, then, in a plane so near that 
of his diurnal motion, and in the same direction, they are all 
apt to be confused together. Such a problem as we have stated 
will, we believe, make the annual motion of the Sun appear, 
as it is, distinct from the diurnal. 

And first we must have a located Observer. Let him be at 
Quito, under the Equator. It is midnight with him at the 2 2d 
of March. Where is the Sun, and when by the annual motion 
of the Earth will he see it ? The Sun is in the first degree of 
the sign Aries ; and of course in the inferior Meridian, while over 
his own head in the superior Meridian, is the place of the Eclip- 
tic which the Earth is in, viz., First of Libra. The Earth must 
move through Libra, Scorpio, and Sagittarius, to the First of 
Capricornus, before the Sun, moving through Aries, Taurus, and 
Gemini, to Cancer, is seen peering above our eastern Horizon. In 
the mean time, all the stars which were on our Meridian at the 



190 A YEAR FOR A DAT. 

beginning of the year have gone directly but gradually down, and 
as the Sun is rising in the east, they are setting in the west, while 
those which were rising as our dreary midnight struck, have 
now (rising at the rate of a month for two hours) come to the 
Meridian. But we see them not, for the Sun is rising. But 
where ? In the Equator, at the point east ? No. For in the 
last three months he has gone in his apparent course from Aries 
to Cancer, and he is rising at his extreme northern declination 
with an amplitude which, at the Equator, equals the declination. 
So the Sun is rising 23^° north of us. 

He is in Cancer. Where will he be (moving now above the 
Horizon) at three months from this time? Directly in our 
Zenith, crossing the Equinoctial, having travelled in the Ecliptic 
from the Summer Solstice to the Autumnal Point. In three 
months more he will have descended to the west in the same 
direction as he rose, and he will be setting at the Winter Solstice 
with an amplitude of 23^° south of the Equator. At the end 
of another three months, he will be in our inferior Meridian, where 
it intersects both the Ecliptic and the Equinoctial. This prob- 
lem will be varied by the different location of the Observer and 
by the different time of the year, or the day, when you suppose 
the diurnal motion to cease. Let every one work it out as re- 
gards his own position, and as many other places as he chooses. 

Suppose, in reference to the subjects of the last chapter, we 
take our staud at Washington, the seat of government for the 
Republic of America, what is the length of its longest day ? 
what of its shortest ? When do each occur ? From the longest 
to the shortest day, how many months in time ? How many de- 
grees of space has the Earth actually, and the Sun apparently 
passed over in going from one Solstice to the other ? At Wash- 
ington will there be another day of the same length as the 1st of 
May ? In what latitude and at what time will the nights be 
equal to the days in Washington at the 10th of May? 



CHAPTER XIX. 

Climates. — Isotherms. — Causes of Exception to the Law that 
Climate is as Latitude. 

1. The climate of any place is the effect of the Sun's 
heat, modified by the various circumstances connected 
with the peculiar position of that place upon the Earth. 



CLIMATOLOGY. 191 

And the great general rule is, that Climate is as Latitude : 
that the greatest degree of heat is at the Equator, and 
the most intense coldness at the Poles, and hence that 
anyplace is wanner in proportion as it is nearer the Equa- 
tor, and the reverse. 

2. Although this grand rule has its exceptions, yet it is 
good to dwell exclusively upon it for a time. In educa- 
tion, the attention of the pupils should not be taken too 
soon or too much from great general truths expressed 
with brevity, to consider long and intricate exceptions. 
The reason why the Equatorial regions are the warmest 
is, that they are so presented to the Sun, that they receive 
his direct rays ; while, from the globular figure of the 
Earth, the parts towards the Poles receive his rays ob- 
liquely ; so that less and less heat, as we go towards 
the Poles, is communicated to the same quantity of sur- 
face. 

3. To illustrate this fundamental principle, we refer you 
to a diagram (see Fig. 30) where, in N. Lat. 42° 23', 
stands an Observer of Boston. In order to show the 
effect of latitude and the contrast of the opposite seasons, 
we have brought two things together, which cannot exist 
together in nature ; for we have but one Sun, and he can- 
not be at the same time in two places. But to show this 
contrast, we submit to imperfections in our figure, which 
we trust will not at this stage of progress give false ideas 
to any of our learners. They know, notwithstanding 
the figure does not indicate it, that the Sun, shining from 
the Tropic of Capricorn on the 21st of June, would shine 
beyond the North Pole to the Arctic Circle, and in the 
same manner to the Antarctic, if he were shining from 
the Southern Tropic on the 23d of December. But 
with all its imperfections, our figure shows strikingly the 
contrast between the Summer position of our Observer, 
when, on the 21st of June, he has the Sun's rays nearly 

Chapter XIX.— 1. What is the Climate of any place ? "What is 
the great general rule concerning Climate ? — 2. What says your 
author concerning the sudden withdrawal of the mind of the 
learner from rules to their exceptions ? Why are the Equatorial 
regions the warmest ? 



192 



RAYS DIRECT AND OBLIQUE. 

Fig. 30. 




vertical, and his Winter position on the 2 2d of Decem- 
ber, when only a few slant rays touch the surface of the 
Earth. 

4. The Earth has heretofore been divided by circles of 
latitude into 30 Climates; 24 from the Equator to each 
Polar Circle, and 6 from each Polar Circle to the Pole. 
In this enumeration, the first 24 are predicated on the in- 
crease of half an hour to the longest day ; and the re- 
maining 6 on the Sun's appearance as being for one 
whole month, present or absent, and so on to 6. This 
division becomes, towards the Polar Circles, on account 
of the Earth's convexity, too minute to be useful. But 
we approve of some division of climates founded on the 
same principle, since, although circumstances, as we shall 
show, modify the great general rule respecting the heat 
of places, yet the length of the days and nights, and the 
appearance of the heavenly bodies, are always in accord- 
ance with the latitude of the place. 



3. Why has your author here introduced a figure ? Name its 
imperfections and its use. — i. How has the Earth been divided 
into Climates ? What is said of this classification ? 



an hour's difference. 



193 



Fig. 31.— Climates. 

Twelve from the Equator to each Polar Circle— differing by length of day—* 
one hour to each Climate. 



24 130 




11 



194 EIGHTEEN CLIMATES. 

5. The Southern Frigid Zone is wholly uninhabited, 
and the Northern nearly. Leaving their six Climates of 
months unaltered,* we will divide the parts of the Earth 
extending from the Equator to the Polar Circles into 12 
Climates of hours, predicated on the increase of one hour 
in the longest day in going from the Equator each way to 
both Polar Circles. Observe the effect of the Earth's 
convexity on these 12 belts or zones, as shown in the 
diagram. The first Climate, or that next the Equator, is 
nearly 17° broad; the second is about 14°; the third, 
10° 36'; the fourth, 9° 36'— extending to^atitude 49°, 
the northern extent of our Republic. After this the belts 
grow narrow very fast, and that next the Polar Circle is 
but two-thirds of a degree in breadth. Probably two- 
thirds of the Earth's inhabitants are contained in the five 
first northern Climates. 

6. Having now noticed Climates as to the general rule 
that they diminish in heat as latitude increases, we shall 
next treat of the exceptions to that rule, with their causes. 
That cause of variation from the rule which it seems to 
us is worthy of the first mention, is the internal heat of 
the Earth. While the surface is cool, fires are raging 
within. If we dig into the Earth to the small distance 
of 80 or 100 feet, the orifice thus far grows colder; but 
if we continue to dig downwards, the internal heat begins 
to manifest itself, and it increases a degree for every 60 
feet wmich we descend. At this rate every substance 
known to man, even granite itself, would be in a state of 
fusion at a distance of 21 miles below the surface. No 

* See Appendix. 

5. Are the Frigid Zones inhabited ? What division into Cli- 
mates is here made \ Make a sketch of the figure on the black- 
board, and give a general account of the countries through which 
the four first Climate lines pass. What do you observe by the 
figure concerning the effects of the convexity of the Earth on 
these 12 Belts or Zones? — 6. What is next to be your subject — 
a rule or exceptions to a rule ? What rule is spoken of? What 
is the first of the causes named of exceptions to this rule ? What 
concerning heat is learned by digging into the ground? To what 
startling conclusion might these facts lead? How far does ac- 
tual knowledge extend ? 



VOLCANOES AND EARTHQUAKES. 195 

depth beyond about 1700 feet has, however, been actually 
tested. 

7. But that there are internal fires and masses of heavy 
matter in a melted state, is abundantly proved by the 
Volcanoes through which they find a constant outlet — 
such as Etna and Vesuvius. Both of these are near the 
sea ; and others, such as Mauna Roa, in the Sandwich 
Islands, rise up from the midst of the ocean. The coldest 
as well as the warmest regions have their Volcanoes — as 
Hecla, in Iceland. The Boiling Springs, which, from the 
bowels of the Earth, send up many feet, and with great 
force, hot water and mud, are phenomena which also 
prove that the Earth has an internal heat, not derived 
directly from the Sun. Such are the Icelandic Geysers. 

8. But the most sublime and terrific of the effects of 
internal fires are felt in Earthquakes. Sometimes the 
solid land shakes like the sea in a tempest, and some- 
times the Earth yawns, and cities sink into the fearful 
chasm. There is good reason for believing that these 
are the upheavings of the crust of the Earth, pressed 
from beneath by some substance suddenly expanded — 
perhaps some collection of water suddenly thrown into 
a great internal fire, and converted into steam. What 
makes this probable is, that Earthquakes generally have 
their origin in the bed of the Ocean. After the great 
Earthquakes at Lisbon and Cadiz, the sea rose 50 and 60 
feet. Earthquakes accompany eruptions of Volcanoes ; and 
but for these outlets, or safety-valves, the internal fires of 
the Earth would doubtless be still more destructive. We 
do not, however, believe, as some seem to suppose, that 
the nucleus of the Earth is a boiling mass of liquid fire, 
because it would be very dangerous, if it were so, to man, 
for whose use the Earth was made ; and it would there- 
fore militate against the wisdom of the God who made 

7. What other proof is there that internal fires exist ? Is 
there reason to believe that these fires are as much under the 
water as under the land ? — 8. "What is the most terrific effect of 
internal fires? Where do Earthquakes generally have their 
origin ? and what is probably their cause ? Why does the author 
not believe that the nucleus of the Earth is liquid fire ? 



196 THE THERMAL EQUATOR. 

it. As far as we can trace the effect of internal fires, 
they have advantages which far overbalance the dangers 
and inconveniences which attend them. 

9. The fact thus established, that the Earth has a 
source of heat in its internal fires, the warmth of climates 
may well be affected by it. There may be inequalities 
in its distance from the surface, in its intensity, or in the 
effect which it may have according as the Earth's surface 
is covered with land or water. Its effects on land will be 
more enduring than on water, for it will not be so easily 
transmitted. The northern Hemisphere has far more 
land than the southern, and, generally speaking, it has 
more heat. The Thermal Equator, or Equator of Heat, 
passes a degree north of the Earth's Equator. The Baron 
Humboldt has found that the snow-line, or line above 
which, on account of the height of the atmosphere, there 
is perpetual snow,* varies in the same latitudes ; and also 
the thermic scale of the cultivation of plants — (i. £., the 
degree of heat necessary for their production) — where their 
height is the same, varies in different parts of the Earth, 
under the same latitude. These facts show clearly the 
presence of other causes of difference of climate than the 
heat of the Sun, though in comparison they are incon- 
siderable. 

10. The Sea is a great equalizer of the Heat of the Land, 
making it cooler in the Torrid regions adjoining, and 
warmer in the Temperate. That the sea, receiving the 
same heat from without, should yet be cooler than the 

* According to Humboldt, the snow-line in the southern de- 
clivity of the Himalayas is 12,962 feet, while in the warmer 
region of Thibet it is 16,630. As a general rule 267 feet 
elevation makes the difference of one degree of latitude. 

9. Is it probable that internal fires affect Climates ? Suppose 
that internal heat exists, is it probable that its action would be 
equal ? How would the land be affected in comparison with the 
water ? Which side of the Equator has the most land ? And 
where is it found that the central line or Equator of heat is ? 
"What is a snow-line ? What a thermic scale of the growth of 
plants? What has the Baron Humboldt observed concerning 
these ? What is proved by these facts ?— 10. What effect has 
the sea on climate ! 



THE OCEAN AND THE AIR. 197 

land in the Torrid Zone, is easily accounted for, by the 
ease with which the particles of water move among them- 
selves, and by the effects of heat and of the gravitation 
of the Sun and Moon, to move and mingle their particles, 
and thus to diffuse to colder regions the heat which it 
receives in the hotter, from the direct rays of the Sun, 
But it is not easy to heat water by communicating caloric 
merely to its upper surface ; and why shall we not be- 
lieve that the Earth's internal fires have an effect to warm 
those waters of the ocean which lie deep in submarine 
valleys ? How else should the climates of those islands 
and countries of high latitudes surrounded by it, be 
much w r armer than others in the same latitude ? We 
know that if any region is intersected and divided by 
seas, gulfs, and bays, it will in its climate experience the 
effects of the mild and equable temperature of the 
waters. Thus Europe, cut into peninsulas by intervening 
waters, is much warmer than the parts of North Amer- 
ica in the same latitude. But western coasts are warmer 
than eastern for another reason. 

11. To understand this, we must consider that at- 
mosphere as well as water has influence on climate. 
Both air and water, when heated, expand, and their par- 
ticles rise : when cooled, the reverse. The central waters 
about the Equator, from this cause, would become lighter, 
and the waters next would press beneath, raising them up 
and forcing them to now out in currents. So the air, too, 
warmed at the Equator, would rise, and the denser par- 
ticles from the north and the south blowing over the sur- 
face of the Earth as the lighter rise to the upper regions 
of the air, there would thus be, in both the atmosphere 
and waters, upper currents towards the Poles, and lower 
currents from the Poles to the Equator. But it is the 

10. Why should it be cooler than the land in the Torrid re- 
gions? But what reason have we to suppose that far from the 
Torrid Zone the sea is warmer than the land ? How does your 
author account for its heat ? What examples of countries affected 
by the proximity of the sea are given ? What is said of coasts ? 
— 11. What besides the sea affects climate? How are both the 
air and the water affected by the Sun's tropical heat ? And 
what currents may be expected to be formed ? 

IV* 



198 THE TRADE WINDS* 

lower currents of the air which are at the surface of the 
Earth, and the upper currents of the water. So the 
lower air blows inwards towards the Equator, while the 
upper waters flow out from it, 

12. These currents in the water, and winds over the 
sea and land (for currents of air are winds), have their 
annual course modified and changed by the rapid motion 
of the Earth at the Equator, as she moves from west to 
east in her diumal rotation. This produces a tendency in 
the air to a motion in a contrary direction— viz., from 
east to west. Its actual motion is therefore between these 
two directions, the wind blowing on the north side of the 
Equator towards it, in a southeast direction (which is a 
northwest wind), and on the south side of the Equator, 
in a northeast direction (which is a southwest wind), 
These great constant currents of air, from the northeast 
and southeast towards the Equator, are called Trade 
Winds, But the direction of the Trade Winds is rather 
in curved than in straight lines, being, as they approach 
the Equator, deflected towards the East. The diurnal 
motion of the Earth affects the winds of the Equatorial 
regions, as there much friction is produced ; but less and 
less as we go towards the vanishing points, the Poles. 

13. Constant winds and currents are diverted from 
their course by various causes. In the Tropical regions 
the land is more heated during the day than the sur- 
rounding waters. The heated air over the land, there- 
fore, rises, and the cooler over the surrounding water flows 
in to supply its place. But during the night the land is 
coolest, and the wind then blows from the land to the 
sea. These are the Land and Sea Breezes, so comfortable 
in the warm regions. The great extent of land which 
in Asia extends into the northern part of the Torrid 
Zone, becomes heated in Summer ; and the whole mass 

12. By what are these currents, which the heat of the Sun 
would cause to blow from the north and the south towards the 
Equator, modified ? Describe the Trade Winds and their causes. 
— 13. Are these constant winds and currents ever diverted from 
their course? Describe the Land and Sea Breezes and their 
causes. 



THE MONSOONS* 199 

of air over the Indian Ocean then blows towards it ; while 
in Winter it blows in the opposite direction, the Sun being 
then in his Southern declination. These winds are called 
Monsoons. The Trade Winds from the north meeting, 
near the Equator, with those of the south, they completely 
neutralize each other, and produce at sea such dead Calms, 
that a candle will burn without flickering. . . It is a well- 
known fact that in the Atlantic Ocean, between Europe 
and America, a southwest wind prevails to such an ex- 
tent, that the passage from New York to Liverpool is 
ordinarily made, in a sailing vessel, in about half the 
time required for a voyage from Liverpool to New York. 
Mrs. Somerville says : " The southwesterly winds so prev- 
alent in the Atlantic Ocean between the 30° and 60° of 
North Latitude, are caused by the upper current being 
drawn down to supply the superficial current, and as it 
has a greater rotatory motion than the Earth in these 
latitudes, it produces a southwesterly wind." 

14. We have here causes developed why the western 
coast of Europe is warmer than the eastern coast of 
America in the same latitude. This southwest wind 
which visits it comes from warmer regions ; and the 
ocean's warmer currents tend to western shores in middle 
latitudes, and not to eastern. Again, the seas of Europe 
opening from the south, rather than from the north, can- 
not introduce the floating ice from the Arctic regions. 
But Baffin's and Hudson's Bay receive down the icebergs, 
and thus become causes of unnatural cold upon the shores 
of North America and Greenland. 

15. The waters of the ocean and the atmosphere are 
doubtless alike in having their entire masses continually 
moved by the disturbing effects not only of heat but of 
gravitation. The atmosphere has probably its Tides as 

13. Describe the Monsoons, What is the cause of Calms near 
the Equator ? To what does Mrs. Somerville attribute the south- 
east winds which blow in the Atlantic Ocean between Europe 
and America ? — 14. What reasons are here given why western 
Europe is warmer than northeastern America in the same lati- 
tudes ? — 15. What resemblance is here noticed between the water 
and the air ? 



200 1SOTHEBMAL LIKES. 

well as the water. The air is more rarified at the 
Equator by heat, yet the barometer shows that its whole 
weight is greater there than at the Poles. This manifests 
greater height, and may be produced in part by the cen- 
trifugal force, since by it even the solid Earth bulges at 
the Equator ; but it may be in part the effect of Aerial 
Tides. 

16. On account of the internal heat of the Earth, and 
the greater density of that portion of the atmosphere 
which rests upon its surface, and which therefore receives 
and retains not only the Earth's heat but a greater por- 
tion of the Sun's, the heat is greater, and the thermometer 
stands higher at the surface of the Earth than at any 
elevation. In ascending high mountains, even under the 
Equator, the air at a certain elevation becomes cool, and 
the grains and grasses of the Temperate Zone are found. 
Another elevation carries us beyond all vegetation, and 
under the Equator, at about 17,000 feet, we come to the 
region of eternal snows. 

17. Snow-clad ranges of mountains depress the tem- 
perature of surrounding countries. Ranges of moun- 
tains so placed as to impede the currents of warm air 
brought from the sea, depress the temperature of places 
beyond, but a contrary effect is produced when ranges 
of mountains impede the access of sharp winds from icy 
regions. Countries with natural marshes and heavy 
forests are cooler, than when by drainage, and clearing 
away the trees, the Sun is admitted to the soil. Many 
springs are then dried up, and water-courses diminished. 

18. The Baron Humboldt has done more than any 
other man in improving what he calls Climatology. Find- 
ing such important exceptions to the division of the Earth 
into Climates of Latitude and Time, he substituted the 
division by Isothermal* LiNES,f by which are to be un- 

* Iso-ther?nal, from two Greek words, signifying equal heat, 
f The Isothermal Lines of Humboldt were, by his personal 

16. Why is the heat greatest at the Earth's surface? What 
occurs at about 17,000 feet elevation under the Equator? — 17. 
Mention some other causes of variations of temperature. — 18. 
What is here said of the Baron Humboldt ? 



RAINY SEASONS. 201 

derstood lines drawn on the map of the icorld, through 
places whose medium heat, as measured by the thermometer, 
is equal. On examining a system of these lines, we shall 
be struck by observing that the Thermal Equator, or 
Equator of heat, which has a mean temperature of 84° 
Fahrenheit, is about a degree north of the Earth's Equa- 
tor, and that of the two Isotherms on each side of it, 
which mark a medium heat of 80°, and include the 
hottest part of the Earth, sometimes the northern, is 
found as far from the Equator as 15°, while the southern 
never ranges farther than the 6th degree of S. Latitude. 
Tropical Africa is the hottest region on Earth. 

19. The most interesting to us of all Isothermal lines 
is that of 50° mean temperature, which is that of New 
York. This line bends north from New York both as it 
goes east and west. Crossing the Atlantic, it traverses 
England to the north of London, whence it bends to the 
southeast as it crosses Europe ; and as it passes on it 
touches the northern confines of the Black Sea. 

20. The Rainy Seasons, where they occur, follow the 
apparent course of the Sun. On the Equator and a few 
degrees each side, there are two rainy and two dry sea- 
sons each year. The rain does not continue through the 
day. About two hours before noon, the sky becomes 
cloudy ; at noon, the rain sets in ; and at sunset the clouds 
disappear. This is not experienced in India, on account 
of the Monsoons. There is more rain in a year falling on 
a Zone a few degrees north of the Equator, than on any 
other equal portion of the Earth's surface. A few coun- 

friend, William C. Wood bridge, copied into his Geography ; — a 
work of authority in Europe, as well as in America. It has 
been recently revised, the late census introduced, and the maps 
altered according to recent discoveries and extensions. 



18. What are Isothermal Lines ? Where is the Thermal Equa- 
tor, and what is its mean temperature ? What account is given 
of the two Isotherms on each side of it ? — 19. What is to us 
the most interesting of the Isothermal Lines? What is said 
of the interior of Africa ? — 20. What is said of the Rainy Sea- 
sons ? Where are they found ? Does the rain fall all day i Where 
are found countries which haye rainless seasons ? 



202 DIRECT AND RETROGRADE 

tries have rainless seasons : such are the northern interior 
of Africa, Thibet, and Mongolia in Asia, and California in 
America. 



EXERCISES. 

The order of the signs of the Ecliptic, as has been often men- 
tioned, is, by definition, from west to east ; and the motion of 
any heavenly body in that course is direct; but if opposite 
(i. e., astronomically speaking, from east to west) — then it is 
retrograde. But we have counselled our learners to use their 
eyes to look at the Heavens, and their imaginations to complete 
circles, and thus to conceive of the parts which they cannot see. 
We must not here confuse our minds by confounding the perma- 
nent astronomical east and west with the movable east and west, 
which depends on the position of the Observer, and which is 
expressed by his Prime Vertical, only just so far as the plane of 
his sensible Horizon is concerned. By the latter on the Equa- 
tor, at one of the Equinoxes, the Sun's motion is one way during 
the day, and the opposite way during the night ; that is, above 
the Horizon it is from east to west, and below the Horizon, in 
the contrary direction, from west to east. And as this makes 
the Sun's apparent daily motion, and that of the other heavenly 
bodies, range from west to east during the night, and from east 
to west during the day, so also, as taught in the last Exercises, 
as regards the Observer, would be the Sun's apparent annual 
motion, should the diurnal cease. For the six months which the 
Sun is below the Observer's Horizon, the apparent motion caused 
by the Earth's real motion through the opposite* signs would be 
from west to east, while in that half of the Ecliptic above the 
Horizon, the Sun's apparent motion through the six upper signs 
would be from east to west. 

These circles of motion thus made according to the System of 
the Observer, half east and half west, while according to the 
System of the Heavens they are all east, are from the nature of 
the case apt to create confusion in the mind, and it is well worth 
one's while to give sufficient attention to the subject fully to un- 
derstand it. Look out upon the circumpolar stars as they re- 
volve around the North Pole. Take note of the position of some 
of the most remarkable of the constellations, as our old acquaint- 
ances, Cassiopeia and the Great Bear, which are in opposite posi- 
tions. Suppose the first to be directly above Cynosura, and the 
last below it. Wait two hours, and then go view them again. 
You will find that the constellation above the Pole has moved 
30° towards the west, while the one below has moved just as far 
towards the east. Hence you perceive that these Heavenly 
bodies, according to the Observer's system, have apparently 
tnoved through the upper hemisphere from east to west, and 



SIGHT, A DIVINE SENSE. 203 

through the lower from west to east, while all real planetary- 
motions have, as astronomically defined, been made in circles 
constantly going from west to east. 

If, while you are making this observation, you hold your watch 
so that its face shall coincide with the plane of your circle of 
latitude, or, which is the same thing, the plane of the Equator, 
then its centre will represent the North Pole, and the point of 
the minute-hand may be taken for a circumpolar star. Suppose 
the action of the pointers reversed, and the minute-hand to point 
east ; then from east through south to west ; and from west through 
north to east again : this pointer will represent the seen motion of 
the circumpolar star ; and in the same manner that of the Sun. 
This, in contradistinction from the astronomical round through 
which the planetary bodies really move, might probably be called 
the geographical east and west ; which, as we have seen, goes on 
with the reversed motion of the hands of the watch, and refers 
to the apparent motion of the heavenly bodies ; whereas the as- 
tronomical round, from west to east, is made in the same direction 
as the ordinary movement of the hands of a watch. 

On the Terrestrial Globe, trace the dividing lines of the third 
and fourth northern climates, and tell what countries and great 
cities they contain. What is the length of the longest day and 
shortest night in each? 



CHAPTER XX. 

Explanation of the Night Figure. — The Educated Eye — Much 
learned by seeing little. 

1. If aught human is endued with a spark of divinity, 
it is an educated eye, with vast and comprehensive 
powers like that of Humboldt, Cuvier, Newton, and the 
two Herschels. An educated eye, leads both the reason 
and the imagination; and its possessor, in seeing little, 
knows much. Cuvier, from seeing one bone of an animal 
of a kind not before recognized, was able to describe the 
species of animal to which it belonged. And the astron- 
omers, Leverrier and Adams, looking upon the Heavens 

Chapter XX. — 1. "What may be said of an educated eye ? 



204: TRIUMPH OF ASTRONOMICAL SCIENCE. 

with an eye astronomically educated, and seeing certain 
disturbances in the motions of the outer planets, pro- 
nounced that a large unknown planetary body existed, 
whose orbit was without all those which were then dis- 
covered. Telescopes were accordingly pointed in the 
direction indicated, and Sept. 25, 1846, the great planet 
Neptune or Leverrier was discovered by Galle, and their 
prediction completely verified. 

2. The education of the eye imparts the power of 
observation, which should commence early. The little 
child should be taught to observe — to refer his time and 
his place to the Sun, and to the direction of the shadows.* 
He should afterwards be taught to observe the rising and 
setting of the Sun at the Equinoxes, as this marks the 
exact points east and west ; and also to examine (through 
smoked glass) the course of the Sun at the days of the 
Equinoxes, in order to locate the Equinoctial in the 
Heavens ; and as soon as he understands angles, he 
should be taught that the angle which the Sun's path 
makes with the Horizon on these days is the angle of his 
co-latitude, and that the distance of the Sun's Meridian 
Altitude from his Zenith is the arc of his latitude. Then 
by night he should be called to observe that the height 
of the Polar Star above his Horizon is equal to his lati- 
tude. A child thus taught to connect what he sees with 
the great truths which he learns, will be gently inducted 
to the vantage ground of science ; and may be expected 

* Many persons having, when children, learned to refer the 
points of compass only to the terrestrial objects around them, as 
the fronting of their father's house, of the village church, <fcc, as 
soon as they lose sight of these objects* are entirely at a loss, 
and form a wrong notion of the points of the compass of the 
place they are in, and they complain that their heads are turned, 
If they had learned to calculate from the Sun, they would not 
have been subject to this great annoyance. 



1. "What examples are given of persons possessing an educated 
eye ? What has been discovered in astronomy by this means I 
— 2. What power is imparted by educating the eye ? What should 
children be early taught ? What may be expected of a child 
thus taught? 



A NIGHT FIGURE. 



205 



in after life, with native talent and habits of industry, 
to occupy some of its most honorable heights. 



Fig. 32. 




3. We here present a simple picture of a night scene. 
It is to aid our learners in this cultivation of the mind 
through the eye ; — to induce them, when they look out 
upon the Heavens, and see the Polar Star, the place of 
the Colures, the Pole of the Ecliptic, and the place of the 
Equinoctial, to exercise their imagination and their rea- 
son to fill out the picture ; that thus, while they see with 
the bodily eye what is above their Horizon, they may 
look with no less assurance through " the mind's eye" 
upon what is below, and thus complete the picture. 

4. We will now fancy a dialogue between a Teacher 

3. What i9 the character of the figure here presented, and 
what is the author's object in presenting it ? 

18 



206 REASON GUIDING IMAGINATION 

who has thus far instructed a docile and intelligent pupil 
in the principles of Astronomical Geography as thus far 
exhibited. 

Teacher. I here show you a small and simple night 
figure, where there is little to be seen, but much (from 
what you have already learned) to be inferred and ima- 
gined. Tell me first what, in the picture, do you see ? 

Pupil. I see the Earth, with a little Observer upon the 
Upper Vertex looking forth upon the night. The plane 
of his Horizon is fancied to be of sufficient solidity to 
intercept the rays of the Sun, which is seen below shining 
from Aries, his direct ray falling upon the Lower Hemis- 
phere. In the opposite and Upper Heavens is a great 
star sending a ray upon the Earth from Libra directly 
opposite to that of the Sun. The places of the North 
and South Poles are faintly indicated by their initial 
letters. Is there in reality a great star in Libra ? 

5. Teacher. There is not ; but as Sir John Herschel 
recommends putting an imaginary star into the Vernal 
Point, I have, on this occasion, taken the liberty to put 
one into the Autumnal Point. Where is this Observer's 
Equator ? 

Pupil. Of course equally distant from both Poles. It 
is, I see, where the direct rays of both the Sun and the 
star fall upon the Earth. I wish to know, whether, by 
the words Aries and Libra on the picture, I am to under- 
stand the signs or the constellations, since both are called 
by these names, and they do not come together ? 

Teacher. First tell me why they are not now together, 
since they once were ? 

Pupil. By the Precession of the Time of the Equi- 
noxes, the place where the Sun came to the Equator at 
that time changed, and went back a little each year, so 
that there was a Retrocession of the Equinoctial Points, 
and this has amounted since it began to be observed to 
30°, or one-twelfth part of the Ecliptic. 

4. Draw the figure, and describe what you see upon it ? — 5. 
iBy what reasoning do you decide where is this Observer's Equa- 
tor ? How can it be shown that the Sun and the star are in the 
signs Aries and Libra, and not in the constellations? 



BY SUGGESTIONS OF SIGHT. 207 

Teacher. This is correct ; and the little picture affords 
you the means of deciding whether the words Aries and 
Libra refer to the signs or the constellations. 

Pupil. I see it now. Both the Sun and the star are in 
the Equinoctial, since their direct rays strike the Equator. 
But Aries and Libra, whether signs or constellations, are 
in the Ecliptic. But there are only two points of con- 
tact between the Ecliptic and the Equinoctial, and these 
are not where the constellations are, but where are the 
first degrees of the signs. The Sun and the star must 
then be in the first degrees of the signs Aries and Libra. 

Teacher. What are these points called ? 

Pupil. The Equinoctial Points. The Sun is in the Ver- 
nal and the star in the Autumnal Point. 

6. Teacher. Where do you understand this Observer's 
Meridian to be ? 

Pupil. From the way in which I have seen other 
figures of this kind drawn, I should judge it to be con- 
centric with the outer circle of the Globe, that being his 
Terrestrial Meridian. 

Teacher, You are right That is the intention of the 
figure, and if you had not made a right guess from the 
probability of the case, I should have told you ; for the 
exterior of the circle is not necessarily the Observer's 
Meridian. But since the maker of the figure intended it 
as such, you are now certain that you are right in con- 
sidering it so. What do you judge to be this Observer's 
latitude % 

7. Pupil. The star is in his Meridian, and it marks 
the place of the Equinoctial. From the star to the 
Zenith, or, which is the same, from the point of its direct 
ray's intersection with the Earth's surface to the Observer, 
is the arc of his latitude. Measuring with my eye, I see 
that this arc of the latitude is not so great by a few de- 
grees as the arc of the co-latitude, from the star to the 
Horizon. I therefore judge this Observer to be in north 
latitude {north, because he is nearest the North Pole), 

6. What in this figure is the Observer's Meridian ? — f J. How 
do you find the probable latitude of this Observer \ 



208 TIME OF THE NIGHT 

somewhere about 42°. Perhaps our grave little Observer 
is one of the Professors of Yale or Harvard College. 

8. Teacher. Since you are called on to exercise your ima- 
gination, it is but fair to allow it all innocent play. But 
whoever this Observer may be, I am now about to make 
some minute inquiries concerning his position. What is 
his day of the month? What is his hour of the day, 
or rather of the night, and what is his minute of the 
hour? 

Pupil. This is very minute indeed. First, what is his 
time of the year ? That is decided by the place where 
the Sun is, and the Sun is in the first degree of Aries at 
the Vernal Equinoctial Point. The time is then the Ver- 
nal Equinox, which now occurs at the 22d of March. 

9. Teacher. Right ; and now you are to tell me what is 
our Observer's hour of the night. Before you answer 
this question, however, I wish you to consider if there 
be not now some important circle of the Heavens coin- 
cident with this Observer's Meridian. 

Pupil. There is. It is the Equinoctial Colure; for 
that is a secondary to the Equator passing through the 
Equinoctial Points, and the Sun and the star are at this 
moment in it, and they are by the figure at the same 
time both in the Observer's Meridian. Therefore, the 
Meridian and the Equinoctial Colure are in the same 
place. I observe you call them coincident ; would it not 
be as well to say they are identical ? 

Teacher. For our present .purpose of finding the time, 
it would make no difference, but when we have disposed 
of the present question, I will show you why they should 
be considered as not blended into one, but as each existing 
and running along together. With them there is in fact 
still another and third circle, whose separate identity 
must also be retained. That is the Observer's North and 

8. How and wherefore do you decide concerning this Obser- 
ver's time of the year ? — 9. How does it appear that there is 
a second circle of the Heavens coincident with this Observer's 
Meridian? What difference is noticed between the terms co- 
incident and identical ? What third circle is coincident with the 
Observer's Meridian and the Autumnal Colure I 



to a iiorora 209 

South Vertical Circle. But we now return to the ques- 
tion, what is our Observer's hour of the night ? 

10. Pupil. Clearly it is midnight; for the star on the 
opposite Meridian to that the Sun is in, passes through 
the Zenith of the Observer. 

Teacher. Is the hour just twelve ? Suppose it wanted 
four minutes to twelve, or was four minutes after ? 

Pupil. In either case the Meridian, in which are the 
Sun and the opposite star, would not be in the Observers 
Meridian by one degree. Four minutes before twelve it 
would be one degree east of it, and four minutes after 
twelve one degree west. So that our Observers time, on 
the supposition that these Meridians are exactly coinci- 
dent, is in reality made out to the minute. 

11. Teacher. And do you not already perceive how 
much you may know by a little that you see, when you 
have a truly educated eye ; for if, from the little which 
you and I know, we can thus multiply the gift of sight, 
how must it be with an astronomer like Sir John Her- 
schel \ 

Pupil. There is, indeed, something very animating in 
the thought that we may learn te know much in seeing 
little, I am thinking as I look at this figure — for this 
exercise, I believe, makes my imagination active — that if 
you will give me the exact place of this Observer in lati- 
tude and longitude, that I will go on with this subject 
still farther, and perhaps accomplish something beyond 
what you yourself at first expected, 

Teacher. This will give me the pleasure of enjoying 
the fruits of my labors. I will give you, then, Troy, in 
New York, as the place of the Observer. Its latitude is 
42° 44' north, and its lonontude is from Greenwich, 73° 
40' west. What do you propose to do ? 

Pupil. You know my fondness for drawing. I now 
give to it two hours a day. I propose to enlarge this 
little night figure, and make it a beautiful and useful pic- 



10. How do you decide this Observer's hour of the night? 
What is it ! Suppose it either lacked four minutes of twelve 
or exceeded it bv four minutes ? 

18* 



210 COINCIDENT NOT IDENTICAL. 

ture ; for since I have now the latitude and longitude of 
the Observer, I shall find no difficulty of filling this 
eastern hemisphere of the convex figure of the Earth, and 
this western concavity of the Heavens above it, with the 
things which really belong to each. I will sketch the 
continents and seas of the Earth, putting them in light 
or shade as they are situated with regard to the Sun. 
In the upper Heavens I will place the most remarkable 
stars in their own appropriate dark ground. I think I 
will introduce the pale Moon a little past quadrature into 
the west. I will take away this fancied Horizon, and 
keep the light of Sun, Moon, and Stars each to its own 
proper place. 

Teacher. It is a good plan, and if executed well, will 
make an admirable picture. If it were but carried out 
with chalk sketches on a blackboard, it would be a very 
useful exercise, and illustrate still farther our subject of 
the wonders which can be wrought out by an educated 
eye. 

12. Pupil. Will you now inform me concerning those 
circles, of which three may be considered as passing over 
the head of the Observer ; his own Meridian, the Equi- 
noctial Colure, and his North and South Vertical. Why 
are they all to be considered, notwithstanding they exist 
together, not as identical, but as coincident, and as having 
each a separate existence ? 

Teacher. Suppose, looking to the Heavens, you point 
your finger to the North Polar Star, then bring it down 
in the line of the Meridian to the point north on the 
Horizon. In what direction will you have moved your 
finger, north or south ? 

Pupil. North, I suppose. I shall have moved it to- 
wards the point north on the Horizon. 

Teacher. Yes, but you will have carried it in a direc- 
tion from the North Pole towards the South. 

11. How may the plan of this Night Figure (the latitude and 
longitude of the Observer being given) be still carried forward 
and made more minute ? — 12. If you move your finger from the 
North Pole along the Meridian to the point north on the Ho- 
rizon, in what direction do you carry it ? 



A CONTRADICTION EXPLAINED. 211 

Pupil, I now recollect your former instructions ; and I 
see that I was wrong, and that it is South. 

Teacher. There is an inherent difficulty in this subject, 
which I? know no other way to dispose of but to consider 
these lines as being distinct, though co-existent ; and to 
decide in reference to the Observer's System that the arc 
in question goes North, since it goes towards the point 
North on his Horizon ; but as to the System of the Earth, 
the same direction being on a Meridian going direct from 
the North Pole to the South, it is South. We see from 
this the necessity of not mingling together and confusing 
different circles, as they may for a time coincide. On 
the contrary, we must maintain for each its separate exist- 
ence and peculiar properties. We shall find occasion to 
remember these instructions in studying the Northern 
Heavens, where the different systems come in perplexing 
contact. 



EXERCISES. 

"It is often of use," says Sir John Herschel, "to know the 
situation of the Ecliptic in the visible Heavens at any instant ; 
that is to say, the points where it cuts the Horizon and the alti- 
tude of its highest point" or, as it is sometimes called, " the none- 
gesimal point of the Ecliptic." Sir John Herschel lays down a 
method of finding this point by joining the elevated poles of the 
three axes of the systems of the Heavens, the Earth, and the 
Observer; but his method requires more mathematical knowl- 
edge than our students are supposed to possess ;* and, besides, 
we believe we can give a more simple and an easier method of 
finding the position of the Ecliptic, especially at night, when the 
stars are visible. 

By the Highest Point of the Ecliptic is meant the Summer 
Point, or that nearest the elevated Pole, and whose meridian alti- 
tude is greatest, and of course having the greatest declination 
(23|°). We know it is on the Summer Solstitial Colure, and 

* A gentleman not behind any other in our country for the union of science 
with the power of imparting it, on examining this work, said to the author, 
" You have done for the young what Sir John Herschel has for the more ad- 
vanced, in bringing down scientific subjects to the comprehension of the un- 
learned.'" That is all the praise I covet. It is the very problem I undertook 
to solve. Few can appreciate its difficulties. 

12. What reason do you find in this to be careful in the use 
of the words identical and coincident f 



212 THE NOHEGESIMAL POINT. 

90° distant from the Ecliptic Pole, that being on the "Winter 
Colure, distant 23£° from the North Pole, and having at 90° 
distance the lowest point of the Ecliptic, or that point (the Sol- 
stitial) which has 23^-° Southern declination. 

We trust our students now know where to look for the Eclip- 
tic Pole and the two parts of the Solstitial Colure divided by the 
Polar Star into the Summer and Winter Colure, By these Co- 
lures, then, the position of the Highest and Lowest Points of the 
Ecliptic may always be known when we look out upon the stars ; 
and these being known, it is easy to decide whereabouts the 
Ecliptic crosses our Horizon, Yet that depends in no incon- 
siderable degree on our latitude ; for suppose, in looking at the 
Heavens, we see Caph in our Meridian, we know that the Ver- 
nal Colure now coincides with it and passes through our Zenith. 
Where is then the Highest Point of the Ecliptic ? It is in the 
Summer Colure, 90° or six hours from the Vernal ; and Summer 
is next after Spring, and the direction of the signs of the Eclip- 
tic are from west to east. The Highest Point of the Ecliptic is 
then six hours or 90° east of us, and the Lowest Point six hours 
west of us. If we live on the Equator, these Colures being 
great circles, and the Equinoctial at right angles with our Me- 
ridian, the Vernal will coincide with our Horizon, and the High- 
est Point will be in the Eastern Horizon, with 234° of Northern 
Amplitude, and the Lowest Point will be in the Western Hori- 
son, with the same degree of Amplitude South ; and the Ecliptic 
will cross the Equinoctial precisely in our Zenith, which now 
coincides with the Equinoctial Point. This is the same case of 
position of the Ecliptic as that supposed in delineating the 
yearly course of the Sun, from Summer to Winter, the Earth's 
rotation being stopped. But to a person not living on the Equa- 
tor, but in north latitude, the points of the Horizon cut by the 
Ecliptic are different ; as a greater portion of the Ecliptic will 
be in the northern hemisphere, and a lesser portion in the 
southern. This you will at once see by taking some latitude, as 
that of Paris, and elevating the North Pole 49°.* Now, observe 
the Triangle of Time, and you will find the Highest Point of the 
Ecliptic is where the vi o'clock Colure meets the Equator, and 
between this and the eastern Horizon there are two lines of 
hour-circles, showing 30° of space ; and the Ecliptic, after stand- 
ing a while at that height above the Horizon, goes not directly 
but diagonally from that Highest or Solstitial Point towards 
the Eastern Horizon, and then meets it with an amplitude of 
about 33° north. As much of the Ecliptic as appears within 
this Triangle on the east beyond the vi o'clock hour-circle, so 
much will fall short of the vi o'clock hour-circle on the west, 
and the Ecliptic will have the same amplitude of 33°, but south. 
But it will fall short of what is above the vi o'clock hour-circle 

* The latitude of Paris is 49° 50'. 



THE HORIZONTAL POINT. 213 

in the east, a quantity equal to the excess there, viz., two hours 
or 30°. If in the problem of the Sun's appearance, the Earth's 
rotation being stopped, we had taken the latitude of Paris in- 
stead of the Equator, this description of the Ecliptic as above 
the Horizon would show the Sun's path through the six months' 
day, and it would show that of the six months which the Sun 
would be above the Horizon, when rising with the Ecliptic as 
here described, four of the months would be between the east- 
ern Horizon and the Meridian, and only two between the Merid- 
ian and the western Horizon. But place the Autumnal Colure 
in the Meridian, which will make the case that of our Observer 
in the Night Figure, after a time will come Winter, and we must 
look east, but at the same time south of the Equator, for the 
Ecliptic, and here we shall find the two hours cut off which 
were in the last case in excess, and the Sun, if rising in the Eclip- 
tic now, with a six months' day before him, would be coming 
from his winter station in the south to his summer station in the 
north, and would have his turning point before his setting, as in 
the other case after his rising. 

Observe the diagram of the climates, and then look on the 
Terrestrial Globe, in north latitude, for the principal countries 
and cities where the longest day is 16 hours, and from that to 18 
hours. What two climates are these, and between what lati- 
tudes ? Look on the Globe for the principal countries and cities 
where the days are 18 hours, and from that to 21. What cli- 
mates are these, and in what latitudes ? What are the lengths 
of the longest days in the three last climates, and what the 
latitudes ? 



CHAPTER XXI. 

Time. — The Common Year. — The Civil Year. — The Sidereal 
Day. — The Sidereal Year. — Astronomical Instruments and 
Observatories. — The Solar Year and Day. — The Astro- 
nomical Year. — The Cause of the difference in Time of 
the Solar and the Sidereal Years. — The Retrocession of 
the Equinoctial Points the Cause of the Precession of the 
Equinoxes. 

1. The Common Year, comprising the 12 calendar 
months, is a portion of Time consisting of 365 days, 5 
hours, 48 minutes, and 47 seconds. The Civil Tear is 
so called, because upon it are predicated all arrangements 



214 THE GRAND UNIT OF TIME. 

connected with the civil law referring to Time. It com- 
mences at the midnight xn o'clock, of January 1st; so, 
that in it, no odd hours and minutes are recognized. It 
has 365 days only, except that every fourth or leap year 
it has 366 days. There is a farther arrangement respect- 
ing the odd minutes and seconds, which will be explained 
in the next chapter. 

2. But what are the Days of which the Common Year 
is composed ? Is each of them, that wonderfully exact Unit 
of Time, marked out by one rotation of the Earth on her 
Axis ? That Unit of time is so exact, that if a million Ob- 
servers, each having a perfect time-keeper, should each 
take any fixed star as it comes to his meridian, and observe 
it as it returns, each would find the same time to have 
elapsed, to the ten-thousandth part of a second. This in- 
variable Day, ascertained to be such by the stars, is called 
the Sidereal Day, But it is not so long by 3 minutes 56 
seconds* as the day which goes to make up the 365 days 
of the Common Year. 

3. As the Sidereal Day differs a little in time from the 
Common Day, so also there is a Sidereal Year, differing 
a little in time from the Common Year. The Sidereal 
Year is determined by the length of time which elapses 
from a certain Star on the Median to the annual return 
of the Observer's Meridian to the same Star. If the 
learner has now conceived of the appearance of the Sun 
during the year, in case the diurnal rotation of the Earth 
was stopped, he can easily conceive of the Sun in the 
Ecliptic as apparently moving from any Star in the Eclip- 
tic round to the same Star again ; and that this annual 
movement would form the Unit of a year's time. 

4. But so overpowering to the senses and the imagina- 

* In strictness, 3° 55'.9 

1. What is the Common Year ? Why is the Civil Year so 
named? When does it begin ? Does it recognize any odd hours 
and minutes ? — 2. How is the Time of the Earth's rotation men- 
tioned ? How may it be known to be an invariable Unit of Time ? 
What is this invariable Day called ? What is its length ? — 3. What 
is the Sidereal Year ? How might the learner conceive of the 
Sun's annual motion as apparently moving from any Star in the 
Ecliptic to the same Star again ? 



SIDEREAL TIME DETERMINED. 215 

tion is the sublime and rapid spectacle presented by the 
daily apparent motion of the heavenly bodies, that it is 
somewhat difficult for the young learner clearly to con- 
ceive how yearly Sidereal Time is determined by the 
Stars. To do this, you must suppose an Observer in some 
definite place, taking his observations at precisely the same 
time. Take our Observer in the night figure, having on 
his Meridian his star in the first of Libra, on the 2 2d 
of September at midnight. The same time in the suc- 
ceeding month he goes forth at midnight to look for his 
Star. He finds it 30° west of his Meridian ; for he having 
moved on the Earth 30° towards the East, there has been 
an apparent motion of his Star as many degrees to the 
West. He goes at the end of the second month at mid- 
night, and finds his Star 60° to the West ; at the end of 
the third, 90° ; and then for six months he loses sight of 
it, while it performs the inferior half of its circle of daily 
time. After that he sees it emerging in the East, and ad- 
vancing towards the West. It is now near his Meridian, 
and he goes every midnight to w r atch for it ; for he wishes 
to know the very second in which it is precisely cut by 
his Meridian. At last, by his instruments, he knows it is 
there, and he notes by his chronometers and by his calcu- 
lations the exact time since he saw the Star on the Me- 
ridian before, and he has now the precise measure of the 
Sidereal Year. 

5. It must strike the mind at once that such minute 
observations on the heavenly bodies cannot be made with- 
out special preparation. But they are of vast importance ; 
and to provide for them, even governments of countries 
make expensive preparations. Observatories — high build- 
ings where can be had the whole unobstructed view of 
the Heavens — are made ; and they are furnished with tel- 
escopes, chronometers, and various other astronomical in- 
struments, which men of great science have invented for 

4. What is the grandest, although the most familiar spec- 
tacle of the Heavens? What effect has it upon our clearly 
conceiving the apparent annual motions? But how must an Ob- 
server (suppose the one on the night figure) do to find the Time 
of the Sidereal Year ? — 5. What must here be apparent concern- 
ing instruments ? 



216 SOLAK TIME. 

the benefit of mankind. The Observatory of Greenwich, 
near London, from which Longitude is ordinarily reck- 
oned, is perhaps the most noted in the world. To the 
great philosopher Galileo, of Italy, is referred the first use 
in Astronomy of the telescope. This was about the close 
of the 16th century. In 1667, Sir Isaac Newton greatly 
improved this instrument, to which that science is so vastly 
indebted. In the last century, Sir William Herschel pro- 
duced his wonderful telescope, 40 feet in length, with 
which he made many discoveries. In our days, Lord 
Rosse, of Scotland, has a still larger instrument, with 
which he discovers objects too minute to be seen with any 
former one. In particular it is to be noticed, that more 
and more stars are discovered, as the telescope has in- 
creased in its magnifying power. 

6. From this digression we return to the consideration 
of Days and Years. We now fully understand what is 
meant by the Sidereal Day, and the Sidereal Year. The 
Solar Day is the Time which elapses between two suc- 
cessive noons or appearances of the Sun on the Observer's 
Meridian. And the Solar Year is the Time which 
elapses between the Sun's centre being on the Meridian of 
the Observer to the return of the same after the Earth's 
annual circuit. The common Year and Day is mean (or 
medium) Solar Time, as measured by a perfect Time- 
keeper, having 24 hours to the day, 60 minutes to the 
hour, &c. The Sidereal Year is not a year of Sidereal 
Days, but of Solar Days. The length of the Sidereal 
Year is 365d. 6h. 9m. 10s. : this exceeds the Common or 
Solar Year by 20 minutes 19 seconds.* 

* Professor Maury, at the Observatory of Washington, has 
recently invented an instrument by which the minutest portions 
of time are distinguished, and they are, by the magnetic telegraph, 
instantaneously transmitted. 

5. What is the great instrument of Astronomy ? By whom and 
when first used ? By whom and when greatly improved ? What 
great telescope was the means of important discoveries? What is 
the largest at present ? — 6. What is the Solar Day ? The Solar 
Year ? What is said of the days which compose the Sidereal Year ? 
What is the length of the Sidereal Year ? How much does it 
exceed the Sidereal Year of mean eommon Time ? 



NICE DISTINCTIONS. 217 

*I. The Astronomical Year is a year of Sidereal days. 
It commences at the noon xn o'clock of the Vernal Equi- 
nox. The Observer, in this case, is supposed to stand not 
on the surface but at the centre of the Earth, and to an 
observer there it would be indifferent whether he reckoned 
his year from a Star or from the Sun : the result would 
be the same ; and in either case his year would have one 
more day, than either the Sidereal or the Solar. The 
Astronomical Year, then, according to which Eclipses are 
reckoned and Longitude calculated, has, of Sidereal days, 
366d. 6h. 9m. 9s. All Observatories are furnished with 
Sidereal Clocks, which divide the Sidereal Day into 24 
hours, and hence the Sidereal Hour is less by about 10 
seconds than the Common Hour, the day being shorter by 
nearly 4 minutes. 

8. The Solar Year has then one day less than the 
Sidereal, while the Solar Day is about 4 minutes longer. 
Why is this ? It is because the Earth revolves annually, 
and rotates daily in the same direction. A day is thus 
lost to the Solar Year ; but absolute Time is the same, 
and this lost day may be considered as divided into equal 
portions, which will give an average of nearly 4 minutes 
more to each of the remaining 365 days : that is, just as 
much, as the mean Solar Day exceeds the Sidereal. 

9. Suppose, for illustration, that the hours on the face 
of the clock were not to be reckoned by the revolving of 
the minute-hand from xn to xn again ; but from the time 
in which the two hands being together at xn o'clock 
shall come together again. Now, on account of both 
the hands going the same way, the minute-hand, after 
getting to the starting point, will have to go several min- 
utes farther before it overtakes the hour-hand, and they 

7. "What is the Astronomical Year ? When does it commence ? 
Where is the Observer supposed to stand ; and what difference, 
reckoning from this position, will there be between the Astro- 
nomical, and the Solar and Sidereal Years ? What is the length 
of the Astronomical Year ? With what are all Observatories fur- 
nished ? — 8. What point to be settled is here put in an interroga- 
tive form? How is the question answered? — 9. Explain why a 
day is lost in number, but in minutes the remaining day is longer 
— by the illustration of the two hands of the clock ? 

19 



218 MOKE DAYS— FEWEB MINUTES. 

are again together. So the Earth, in her daily revolu- 
tion, when she comes to the initial point of any one day, 
finds not the Sun just where she left him, but advanced 
one day's course in the Ecliptic, and she must go on until 
she overtakes him, before the day is accomplished. Since 
the degrees of the Circle of the Ecliptic are 360, and 
the days of the year 365, this is nearly a degree to a 
day, and a degree in space corresponds to four minutes 
in Time ; so that if on any day the Earth should begin 
her axial rotation with the Sun and a Star under any Ob- 
server's Meridian, when this Meridian, having swept the 
Heavens, comes again under the Star, completing the Side- 
real Day, the Earth must turn four minutes longer and 
nearly a degree further before the Meridian would come un- 
der the centre of the Sun, and thus complete the Solar Day. 

10. For the Meridian of any Observer to be under the 
centre of the Sun, is but another expression for noon. At 
this time any object placed perpendicularly to the surface 
of the Earth, will cast a shadow (except at the Equator) 
which will be a North and South line. But this is Solar 
Noon. Mean Noon is the Day-xn of a perfect clock. 
The difference between Solar and Mean Noon will be ex- 
plained in the next Chapter. 

11. Any Observer keeping the same place on the Earth, 
and reckoning his day from one Solar Noon to another, will 
have in his year one day less in number than there are of 
actual rotations of the Earth or Sidereal Days ; but he will 
have four minutes more time in each day. This effect will 
be doubled if the Observer, instead of remaining stationary, 
goes round the Earth in the year, travelling from West to 
East. In this case he will neither have the 366 Sidereal, 
nor the 365 Solar Days in his Year ; but he will have 364 
days, and these days, instead of being 4 minutes longer 
than the Sidereal, will be twice that number. If another 
traveller should start from the same place, at the same 
time, and go round the Earth during the same period, he, 

10. What is noon! What is said of shadows at noon? What 
kind of noon is it where shadows fall thus ? What is Mean Noon f 
—11. With what assertion does the 11th paragraph commence? 
How is this illustrated by two hands of the clock. 



TWO TRAVELLERS. 219 

instead of having to overtake the Sun, would meet him 
a little before his full Circuit was completed. He would 
gain a day. If the two travellers should meet on their 
return, they would, by their journals, find themselves two 
days apart. While the one who went East would call the 
day Monday, the one who went West would call the same 
day Wednesday, he having had two da} r s more in his 
year. Yet each has had the same number of minutes ; so 
that if he who went East had two days less in his year, 
he had eight minutes more in each day. 

12. We refer again for illustration to the hands of a 
clock. Suppose two clocks stand side by side, one with 
the hands moving in the ordinary manner, and the other 
with the minute-hand so arranged as to move in a direc- 
tion contrary to the hour-hand. Then let both clocks 
have their two hands together at the upper xn. As they 
move around to the same xn again, the one where the 
minute-hand goes the same way as the hour-hand will 
not have overtaken it by several minutes, whereas the one 
which went the contrary way will have overtaken and 
passed it, by the same number of minutes which the other 
falls short. We take a year as the time of the traveller's 
going round the Earth, because we wish to compare the 
effect with the Solar Day, as losing in the same way a 
day in the year, and gaining about four minutes in a day. 
But there is no necessity of stating the traveller's time as 
a year. If he goes round the Earth eastward, in what- 
ever time, whether half a year or two years, he loses a 
day ; but he gains minutes in his day, according to the 
time — if half a year, then 8 minutes a day ; if two years, 
then 2 minutes a day ; and the reverse, if he travels round 
the Earth westward. 

13. Having disposed of the question concerning the 

12. What will occur to the traveller who goes round the Earth 
the same way in which she revolves on her axis ? What to him 
who goes the opposite way ? Suppose both set out on the same 
day and return the same day, one having gone round the Earth 
East, the other West ? How is this concerning the two trav- 
ellers illustrated by the hands of 2 clocks ? Why is a year men- 
tioned as the time of the two travellers 1 



220 RATE OF RETROCESSION. 

difference between the Solar and Sidereal Day, we come 
now to inquire why the. Sidereal Year is longer by 
20 minutes 19 seconds than the Solar. This is owing to 
the slight movement formerly mentioned of the System 
of the Earth upon the System of the Heavens. By means 
of this, the Equinoctial Points very slowly retrocede in 
the Ecliptic. That is, the Sun every year comes to the 
Ecliptic a little east of his former place. But by defini- 
tion, the Sun's place is the Ecliptic ; and the Equinoctial 
Points must be where the two Great Circles come to- 
gether ; and therefore this retrocession of the Equinoctial 
Points can only happen by the one System moving back 
upon the other. 

14. The effect of this retrocession of the Equinoctial 
Points is to make the Solar Day shorter than the Side- 
real. For the Solar Year is completed at the noon of 
each succeeding Vernal Equinox, the time when the day 
is exactly equal to the night all over the Earth. And 
this time must occur when the Sun's circle of daily mo- 
tion coincides with the Equator. So that if the Sun's 
place, when the Equinoxes occur, is pushed back in the 
Ecliptic, the time will, on this account, be pushed forward. 
That is, so much angular space as the Equinoctial Points 
retrocede, so much yearly time the Equinoxes will precede. 

15. The space on the Ecliptic thus annually retroceded 
is a little less than one second of a degree,* while the 
time preceded, or the Precession of the Equinoxes, is 20 
minutes 19f seconds. Small as are these portions of space 
and time when taken for one year, yet as years accumu- 
late, their effects become very apparent, and cause great 
annoyance to astronomers, as it obliges them from time 
to time to reconstruct their tables of the Latitude and 

* 50".10. t 20m - 19 - 6s - 

13. With what inquiry does the 13th paragraph commence? 
How answered ? What is said of the Retrocession of the Equi- 
noctial Points ? — 14. Explain the effect of the Retrocession of the 
Equinoctial Points. — 15. What is the yearly angular amount of 
the Retrocession of the Equinoctial Points ? What is the amount 
of time of the annual corresponding Precession of the Equi 
noxes f 



GREAT CYCLE OF 25,860 YEARS. 221 



Right Ascension of the Stars. The Vernal Equinox is 
made the initial or Zero Point both of Celestial Longitude 
and of Right Ascension ; and both are reckoned in the 
order of the Signs quite round the whole 360° of the 
circle. The Vernal Colure is that Secondary of the 
Equator, from which Right Ascension is reckoned, and 
the First of Aries, that Secondary of the Ecliptic, from 
which is calculated Celestial Longitude. As all these are 
moved eastward — since the stars move west — then their 
Longitude and Right Ascension increase with and as the 
removal ; and astronomers are, after a course of years, 
obliged to reconstruct their tables. Every thing, how- 
ever, is now understood and calculated upon. 

16. The Retrocession of the Equinoctial Points has 
carried* back the Signs since the time of the early astron- 
omers 30°, so that the first degree of the sign Aries is 
now in the first of the constellation Pisces. In 25,868 
years, the Equinoctial Points, retroceding at the rate 
mentioned, will accomplish a complete circuit of the 
Ecliptic. The two Colures will in that time successively 
sweep over every star in the Heavens. 

The Solar Year, thus reckoned from one Equinox to the 
same Equinox again, and from one Tropic to the same 
Tropic again, is sometimes called the Equinoctial Year, 
and more frequently the Tropical Year, From the year 
thus obtained is reckoned the Common or Civil Year, 
and also the Astronomical. They are all therefore 20 
minutes 19 seconds shorter than the Sidereal Year. 



15. Why does the Retrocession of the Equinoctial Points 
change the Celestial Longitudes and Right Ascension of the 
Stars? What inconvenience is thus given to astronomers? — 
16. How many degrees have the Equinoctial Points receded 
since the days of the early astronomers ? What time, at the 
rate of angular motion at which they now move, will be re- 
quired to complete the circle of the Ecliptic ? What is said of 
the Colures may be predicated of every Secondary, both of the 
Ecliptic and the Equator — What is it ? 

19* 



222 TWO SPHERICAL SYSTEMS. 



EXERCISES. 

Astronomers refer the Precession of the Equinoxes to the re- 
volving of the Pole of the Equator about the Pole of the Ecliptic ; 
but having, by our definitions, connected in one Spherical System 
the Axis and Equator of the Earth and their appendages ; in an- 
other, the System of the Heavens — the Ecliptic and its Axis, and 
their appendages — we conceive it more correct as well as far more 
expressive, to say that the System of the Earth moves upon the 
System of the Heavens ; because by the motion, all belonging to 
the one System changes its place as regards all belonging to the 
other. 

Suppose, for illustration, an ingenious lad, who understands the 
distinction between the Systems of the Earth and the Heavens, 
shall have got up, with wire and strips of tin, a rude piece of ap- 
paratus,* to illustrate this knotty point. He holds it in his hands. 
It represents two Spherical Systems combined. The outer, that of 
the Heavens, and the inner, that of the Earth. Each has its Great 
Circle, Poles, and two Secondaries, crossing at right angles at the 
Poles. Those Secondaries on the Earth's, or inner System, are 
the two Colures dividing the Equator, as they cross it at right 
angles, into four equal parts. Those Secondaries on the System 
of the Heavens, or outer System, are circles of Celestial Longi- 
tude, cutting the Ecliptic at right angles. First let the two Sys- 
tems coincide, axis with axis, and secondary with secondary. 
Then keeping one of the secondaries together for a bond of union 
between the two Systems, slide them upon each other, until the 
axes make opposite vertical angles with each other of 23^° ; that 
being the actual angle, and the measure of the arc between the 
Poles of the two Systems. 

The two coincident secondaries, in which are the Poles of both 
Systems, are the Solstitial Colnre and the First of Cancer. 
The other two secondaries, representing the Equinoctial Colure, 
from which is reckoned right ascension, and that secondary of the 
Ecliptic, from which is reckoned Celestial Longitude (the First of 
Aries), make with each other an angle equal to that made by the 
axes, and also that made by the two great circles, the Ecliptic and 
the Equator. For, as on the Solstitial Colure, the two axes were 
drawn apart 23 J degrees, the same angle must be made by their 
Great Circles, so that wherever the Solstitial Colure is, trace from 

* If these new arrangements of the combined Spheres should be regarded 
as furnishing a permanent improvement to this department of educational 
science, some maker of apparatus will doubtless furnish us with the three 
spheres combined. The old Armillary Sphere will show that it may be done. 
The piece of apparatus which we contemplate would, however, be less com- 
plicated, though far more useful : perhaps not less difficult to make, but ea- 
sier to understand when made. 



USEFUL APPAEATUS. 223 

the Pole of the Heavens through the Pole of the Earth, and there 
you must find the highest point of the Ecliptic advanced 23^-° to- 
wards that Pole ; or if you trace from the Pole of the Ecliptic op- 
posite to the Pole of the Earth, there you must find the extreme 
opposite or lowest part of the Ecliptic, pushed 23J° beyond the 
Equator. 

Now, with your ideas perfectly clear concerning these two Sys- 
tems and their connections, you will find it easy to understand the 
Retrocession of the Equinoctial Points. Keeping the axes of the 
two Systems at the same central angle, slowly revolve the axis of 
the Earth's System around that of the Heavens, and in a direction 
contrary to the rude signs which we suppose placed on your 
Ecliptic. At once that Secondary of the Ecliptic which has, by 
coinciding with that of the Equator, formed the Coincident Circle, 
must be left behind, and the Ecliptic must, for the connection with 
the Solstitial Colure, furnish another Secondary farther to the west ; 
and still another to coincide with the Equinoctial Colure, and 
their intersection crossing the Ecliptic and the Equator, forms the 
Equinoctial Points, which thus retrocede, causing the Equinoxes 
to precede, and the Vernal to meet the advancing Sun 20m. 19s. 
before the yearly Sidereal Circuit is accomplished. 

On the Terrestrial Globe give a general account of the parts of 
the Earth which lie in the first northern climate, ending where the 
longest days are 13 hours. Give a general account of the parts 
of the Earth comprised in the first southern climate. Which cli- 
mate contains the most land in the Eastern Continent ? Which 
in the Western ? 



CHAPTER XXII. 



Irregularity in the Time of Solar Days. — The Mean Day 
found by the equation of tlme, and measured by the clock. 
— Two Causes of the Inequality of Solar Days. — Obliquity 
of the Ecliptic — The Earth's unequal Motion in her Orbit 
performing equal Areas in equal Times. — Disposal of the odd 
Hours and Minutes of the Solar Yeas. — Reformations of the 
Calendar. 

1. At first thought nothing seems easier to understand, 
than the import of the word Year and the word Day. But 
we have already seen that the subjects are complicated ; 
nor are we yet through with their intricacies. We men- 
tioned in the last chapter the Mean Solar Day. That 



224 MEAK> OB CLOCK TIMS, 

there should be a Solar Day of mean or medium length, 
implies that Solar Days are not all equal. From one so- 
lar noon to another the time varies constantly, and the 
longest Solar Day has just half an hour more time than 
the shortest But it is necessary for the daily avocations 
and labors of mankind that there should be a common 
standard of daily time. Learned Astronomers, then, find- 
ing by observation the exact length of every Solar Day in 
the year, have, by working out an important problem call- 
ed the Equation of Time,* found the Mean Solar Day ; 
which is of just such a length that 365 such days, with 
an allowance for Leap-Year, and the other odd minutes 
and seconds, exhausts all the minutes of the tropical com- 
mon year. 

2. The clock, one of the most useful of human inven- 
tions, is made (unless when used for astronomical pur- 
poses) to keep mean solar time of 24 equal hours to the 
day. A clock perfectly regulated is therefore the true 
standard and exponent of mean solar time. The mean 
or medium day of 24 hours haviag been thus established, 
tables are made out, which are found in every common 
almanac, and by which is shown, the agreement or dis- 
agreement of each Solar Day in the year, with the clock, 
that is, with mean time. If it is said that on such a day 
the Sun is so many minutes " slow of the clock," then we 
know that solar noon comes on that day so much later 
than mean noon. If it said, on the contrary, that the 
Sun is "fast of the clock," then on that day Solar or ap- 
parent noon comes so many minutes sooner than mean 

* Equation from aquo, to make equal. Has not the expres- 
sion Equation of Time been perverted from its original and prop- 
er use ? 



Chapter XXII- — 1. What is implied bj the expression, Mean 
Solar Day? "What is said of the inequalities of solar days? 
"What is that problem called by which the mean solar day is 
found ? By what is mean solar time kept ? — 2. If you had a clock 
which kept perfect time, and a noon-mark showing apparent time, 
could you decide for yourself whether the sun was fast or slow 
of the clock ? If your clock stopped, how could you set it by 
the noon-mark ? 



DIFFERS FROM SOLAR TIME. 225 

noon. Suppose the family clock to be stopped, and you 
wish to set it at noon by the noon-mark ; you must first 
consult the almanac. If that tells you that the Sun on 
that day is 10 minutes fast of the clock, you must set 
your time-piece, when it is noon by the mark, at 10 minutes 
after xn ; but if slow of the clock, then so much earlier. 
The clock, it must be recollected, is not to keep solar or 
apparent, but mean time. 

3. There are four days of the year when the Sun is on 
the meridian precisely at the time when a perfect clock 
strikes xn. These are the 15th of April, the 15th of 
June, the 1st of September, and the 24th of December. 
The difference of the sun and clock is the greatest on the 
11th of February, when the Sun is 14^ minutes slow of 
the clock, and the 1st of November, when the Sun is 16^ 
minutes fast. The difference between the longest and the 
shortest Solar Day is thus found to be 30m. 45s., a little 
more than half an hour. But why should the Solar Days 
be unequal, since the times of the Earth's diurnal rotation 
are equal even to the minutest fraction? To understand 
fully why this is so, requires a profound knowledge of 
Astronomy ; but a partial understanding of an important 
subject, if correct as far as it goes, is profitable, as leading 
the way to its future comprehension. In nature we have 
the dawn of the morning before the radiance of the day. 

4. The cause of the inequality of the Solar Days, since 
it is not in the time of the Earth's diurnal revolution, 
must be looked for, and will be found in the only addi- 
tional increment of daily time, viz., that which comes from 
the minutes of the lost Sidereal Day, and is connected with 
the Earth's yearly progress, as day by day she proceeds 
from west to east in her orbit, in the same direction as that 



3. How is the point, to be next discussed, here expressed ques- 
tion-wise? Does your author suppose that nothiDg should be 
learned of a subject unless it can be fully understood ? — 4. What 
increment, or item of increase, is the only one added to the side- 
real day to make up the solar ? In what is the inequality in the 
length of the solar day? Explain (referring to the last chapter) 
what is said of that sidereal day, lost to the solar year, and ita 
minutes added to the remaining days ? 



226 TWO CAUSES 

in which she turns on her axis. This is made manifest 
by the corresponding apparent motion of the Sun in the 
plane of the Ecliptic, with which the plane of the Earth's 
orbit is coincident. 

5. The Sun's Circles of Daily Motion, as divided by 
the 24 Hour Circles* of the Globes, are the same, as re- 
gards the division of time, as if they were all performed 
in the Equator. Suppose you had a globe six feet in di- 
ameter, which, instead of 24 equal divisions, by longitu- 
dinal lines should present 365. Now if the Earth's orbit 
coincided with that of the Equator, and the motion of the 
Earth in her orbit was uniform, then just one of these 
equal spaces (there being 365) would be passed over in 
each day ; that is, all in exactly the same time, each with 
each ; and in that case the Solar Day would be as uniform 
in length as the Sidereal. But the common plane of the 
Earth's orbit, and that of the Ecliptic, is oblique to that 
of the Equator ; and the Earth's motion in her orbit is 
not uniform ; and these are the two causes of the ine- 
quality in the lengths of the Solar Days. 

6. To be convinced that the obliquity of the Earth's 
orbit, and consequently that of the Ecliptic to the Equa- 
tor, is a cause of the inequality of the Solar Days, we have 
but to examine the divisions on the Globe by the 24-hour 
circles. Look at the Equinoctial Colure and the two-hour 
circles next, each side, and your eye will at once inform 
you that they cut o£F longer parts of the Ecliptic than of 
the Equator ; but the Ecliptic and the Equator being both 
great circles of the same sphere, are equal ; and since these 
Hour Circles divide both into 24 parts, the whole 24 parts 
of the one must be equal to the whole 24 parts of the 

* Rather, 24 Hour Semicircles. 

5. How many longitudinal divisions of time are on the globe ? 
How do they cut the sun's circles of daily motion ? What sup- 
position is made as to a larger globe, and an added number of cir- 
cles ? Under what two conditions would the solar days be equal ? 
What then are the two causes why the solar days are not equal % 
— 6. How may we satisfy ourselves that the obliquity of the 
Ecliptic to the Equator is one cause of the inequality in the 
length of the solar days \ 



OF DIFFERENCE. 227 

other. Hence, when adjacent to the Equinoctial Points, 
the parts of the Ecliptic are seen to be the longer of the 
two,* we know that on the other portions of the Globe 
they must be as much shorter.f This reasoning would 
be the same, if instead of 24, there were the supposed 
large Globe with 365 longitudinal divisions, cutting the 
Equator and all circles of daily time into so many equal 
parts. If any two of these longitudinal lines intercepted 
a portion of the Ecliptic exactly equal to the correspond- 
ing intercepted portion of the Equator, then solar time 
would be on that day (what day would be decided by the 
Sun's place in the Ecliptic) equal to mean time, but if the 
intercepted part of the Ecliptic was shorter than that of 
the Equator, then that day would be shorter than mean 
time. Thus is proved that the obliquity of the Earth's 
orbit to the plane of the Equator is one cause of the ine- 
quality of the length of Solar Days ; and the preceding 
calculation proceeds on the supposition that it is the sole 
cause, which is not the case. 

7. For of this irregularity there is a second reason, viz., 
the want of uniformity in the velocity of the Earth's an- 
nual motion. We are here to consider that the orbit of 
the Earth is not a circle, and although the Ecliptic is ap- 

* The Equator with its secondary makes aright angle, of which 
the Ecliptic being the hypotenuse, must be longer than either 
side. By the convexity of the globe, the parts of the Ecliptic near 
the solstitial points would be shorter than the corresponding por- 
tions of the Equator : — parallel lines of latitude at that distance 
are perceptibly so. 

f And when we look at the parts cut off by the hour-circles 
adjacent to the Solstitial Coiure, we perceive that here the Eclip- 
tic is almost like a straight line parallel to the Equator, and of 
course, being at the distance of 23i°, the two lines (surface spaces 
between secondaries) are less in breadth there, than at the 
Equator. 

6. How would the reasoning apply if longitudinal lines divi- 
ded the Ecliptic and Equator each into 365 equal parts? When 
would solar and mean time be equal ? "When would solar time 
be less than mean time ? when greater ? What case is here sup- 
posed ? — 7. What is the second cause of the irregularity of the 
solar days ? 



228 



EQTJAL AREAS IN EQUAL TIMES. 



parently such, yet the Sun's motion there is only apparent, 
and caused by the real motion of the Earth in her ellip- 
tical orbit ; where she moves with what may be called a 
regular irregularity, for it is an inequality of motion ; 
faster in some parts of the orbit, and slower in others ; 
but yet according to a certain determinate law, which is 
found to prevail with all the heavenly bodies. Univer- 
sally they are found to describe equal areas in the plane 
of their orbits in equal times. This law was discovered 
by the great astronomer Kepler, by whom it was first 
taught that the Earth's orbit was an ellipse. 

8. Without attempting to explain the beautiful mathe- 
matical demonstration by which the law of " equal areas 
in equal times." is perfectly proved, we will merely show 
what the words which announce it mean, and how this 
law affects our present subject. 
You see in this diagram an 
oval figure, representing the 
Earth's elliptical orbit, with 
s the Sun in one of the foci ; 
and you perceive that the fig- 
ure is divided into eight trian- 
gles, meeting in the centre. 
These 8 triangles are equal in 
area each to each. Those ad- 
jacent to s b the shorter axis, 
are shorter triangles than 
those adjacent to sa the longer 
axis; but these are as much 
broader as to make up the 
deficiency. And to obtain this requisite breadth, you per- 
ceive that the arcs subtending these equal triangles, are 
very unequal ; b d being much longer than a c. 

9. Now these equal triangles are the equal areas men- 




7. What are we here to consider ? What is said of the mo- 
tion of the Earth in her orbit? What is universally true of the 
moving heavenly bodies ? By whom was this law discovered ? — 
8. How far does your author attempt an exposition of " Kepler's 
law ?" Draw the figure, and explain it as far as it may be under- 
stood by our description. 



VELOCITY WHERE THE GREATEST. 229 

tioned ; and however unequal are the arcs, the Earth, in 
her annual revolution, passes over these arcs in equal 
times. An imaginary straight line from the Sun to the 
Earth, called the Radius Vector, is supposed to sweep 
the plane of the Earth's Orbit as she moves in its ellipse, 
cutting off these equal areas of space in equal times of 
motion. To do this, we see that the Earth must move 
the faster the nearer she approaches the Sun, and the re- 
verse. That is, velocity is inversely as distance, not merely 
in a simple, but in a compound ratio. Hence comes the 
great law to which all bodies moving around a central body 
in space are subject ; viz., that the velocity of any heavenly 
body in its orbit is inversely as the square of its distance 
from the central body. 

10. When the Earth is at b, its Perihelion or least 
distance from the Sun, its motion is so rapid as to make 
the Sun, in the opposite part of the Ecliptic, appear to 
move in 24 hours over an arc of one degree and one min- 
ute ; whereas when it is at a, its Aphelion, or greatest dis- 
tance, his motion in the same time falls short of a degree 
by three minutes. The Earth is known to be at its Peri- 
helion by the measure of the Sun's apparent diameter, which 
is then the greatest ; and it is found, by observation, to have 
its o-reatest angular diameter the 3d of December. The 
Earth is then 3,000,000 of miles nearer the Sun than in 
the opposite part of the year ; but its more rapid motion 
hinders, in some measure, the Sun's effects. Thus a hand 
may be passed rapidly by a hot fire, when, with a slow 
motion, its heat could not be borne. 

11. Thus have been shown two causes ; first, the obliquity 
of the Earth's orbit ; and second, her unequal motion in 

9. What is the Radius Vector ? "What do we learn — from the 
fact that the Earth passes over these unequal arcs of the equal 
triangles — of equal areas in equal times ? What is the great 
law by which the motions of the heavenly bodies are regulated ? 
— 10. What is the rate of the Earth's angular motion per day 
when in her Perihelion ? When in her Aphelion ? At what time 
in the year is the Earth in her Perihelion ? What effect has the 
greater rapidity of motion on the degree of heat derived from the 
Sun ? How much nearer is the Earth to the Sun in Winter than in 
Summer 'i How is it known when the Earth is nearest the Sun ? 

20 



230 A LUffATIOff. 

it, — why that increment of daily time, whose average is 
about four minutes, affects the Solar Days so very une- 
qually. Since the longest Solar Day is half an hour 
longer than the shortest, to perform the Problem of the 
Equation of their Time, it becomes necessary, in order to 
find the true medium, to borrow for the shorter days the 
excess of the longer. A traveller, in going round the 
Earth, in just a year would have the increment of four 
minutes added to each day, on account of the one day 
which he would lose by going east. But this time which, 
by the Equation, has a medium of four minutes a day, 
would, if the circumnavigation of the globe were made in 
a year, actually be, as respected the days, very unequal. 
Whenever he stopped, or went very slowly, the time would 
unduly accumulate ; whereas, whenever he travelled very 
fast, it would fall short of the due proportion. 

12. A natural month, called also the Lunar Month, is 
the time of the Moon's revolution around the Earth. 
There is in this case also an addition to the time of com- 
pleting the full revolution, on account of the Moon's mov- 
ing round the Earth from west to east, in the same way 
that the Earth is moving round the Sun ; and the time 
added is much greater in proportion. The Sidereal 
Month — that is, the time of the Moon's passing from any 
starxtill it returns to the same star — is 27^- days. But she 
must go on to overtake the Earth. If the time of the 
Moon's being seen with the star was a conjunction, and 
she a new moon, she will not be a new moon again until 
she has travelled more than two days, and nearly 30 de- 
grees after returning to the star. From new moon to new 
moon again, is called the lunar Synodical Month, and its 
time is 29d. 12h. 44m. The Lunar Month, as a division 
of the civil year, would be inconvenient ; as the number 
13, into which it divides the year, is an odd number, and 
besides, this division of the year is not exact. 

11. Repeat the two cauees of the inequality of Solar Days. 
By what is the medium day found ? What comparison is here 
made for illustration ? — 12. What is a natural month ? What is 
a Sidereal month, and what its length ? What is the Synodical 
month, and what its length— and its difference from the Sidereal ? 



LEAPING OVER TIME. 231 

13. Therefore, by common consent, the year is divided 
into 1 2 months, the full time of which exactly corresponds 
with the year, which always begins on the first day of 
January. 

This division is doubtless the best possible. The num- 
ber 12 agrees with the signs of the Ecliptic, and being an 
even number, aliquot parts of the year are easily expressed. 
Thus we speak of the summer half and winter half of the 
year, or more definitely of its quarters, the four seasons. 
Annual time is also readily referred to the correspondent 
angular motion of the Sun in the Ecliptic ; 30° being a 
month, 90° three months, and 180° six. 

14. The standard, or tropical Solar Year, has, as we 
have seen, 365 days, 5 hours, 48m. 47s. But the year 
recognized by the civil law has no odd hours or minutes. 
How are these disposed of ? They are, in the first place, 
cleared off, or leaped over, by Leap-year, which, once in 
4 years, adds a day to February, the shortest month in the 
year, thus making that a year of 366 days. But this is 
getting along in time a little too fast ; for the odd time is 
not quite 6 hours, or a quarter of a day, but it lacks 11 
minutes and three seconds. This, in a hundred years, 
would amount to three-quarters of a day. Hence, in the 
rule adopted by Pope Gregory, Leap-year is to be omitted 
at the end of the century. But this would advance the 
beginning of the year too far by a quarter of a day ; 
which, in four centuries, would become a whole day. 
There is not, therefore, by the Gregorian rule, to be any 
leap-year at the close of the fourth century. 

: 15. If these odd hours and minutes were not provided 
for, but the Civil Year reckoned merely by 365 entire 
days, one year would begin before its predecessor had 



13. "What then is the month of the common year? "What rea- 
sons are given for supposing this division the best possible ? — 
14. What difficulty arose in former days with respect to chronol- 
ogy, and how was it disposed of? After Leap-year was added, 
what difficulty still remained ? How was this difficulty met by 
the rule of Pope Gregory? — 15. Explain how, without the odd 
hours being provided for, the calculations of time run into con- 
fusion. 



232 THE CALENDAR REFORMED. 

closed by the return of the Sun, and too soon by nearly a 
quarter of a day each year; the Equinox would thus 
come later and later in the Civil Year, at the rate of 
about one day in four years. Thus all calculations of 
Time would run into confusion. This was once the case, 
as we are informed in ancient history. Julius Caesar has 
the honor of partially reforming the Calendar. He re- 
stored the Equinox to its original place, and added the 
Leap-year. But the odd eleven minutes and three sec- 
onds, by which the true reckoning was exceeded, ran on ; 
and, in a hundred years, amounted to 18 hours, or -| of a 
day ; and, at this rate, advancing the Equinox. In a 
thousand years, this advancement amounted to *l\ days. 
It is known that in a. d. 325, the Vernal Equinox oc- 
curred on the 21st of March. In 1582, it had gone back 
to the 11th of March — 10 days. Pope Gregory XIIL, 
again in 1582, reformed the calendar, setting back the 
time — reckoning the Equinox to be on the 21st of March, 
and establishing the rule mentioned — by which the years 
will no more run into confusion. 

16. This reformation was not at once adopted through- 
out Europe. The reception of the Gregorian Calendar by 
England did not occur until 1652, when eleven days were 
added to bring the Equinox to the 21st of March. The 
3d of September, 1752, was by Statute reckoned the 14th. 
This was accompanied by another alteration in the Calen- 
dar. The 25th of March had been till then regarded as 
the beginning of the year, — which, from this time, was 
to be reckoned as beginning on the 1st of January. The 
new method of reckoning was called New Style (N. S.) ; 
and the former, Old Style (O. S.). Hence arose in the 
dates of that period many cases of utter, confusion. 
Some persons attached to old ways would not use the 



15. What was first done to relieve this confusion of the Calen- 
dar, and by whom ? Explain what occurred after the amendment 
of the Calendar by Julius Csesar ? What was done by Pope Greg- 
ory, and when ? — 16. When was the Gregorian Reformation 
adopted in the land of our forefathers, and what change was 
made in current time ? What other change, which had no con- 
nection with this, was made at the same time ? 



THE TWICE-DOUBLE STAR* 233 

New Style ; while others, unduly zealous in its favor, car- 
ried it into the past. Thus the legal English date of 
those times is said to have been the New Style, while the 
historical date was the Old. It is not unusual to see both 
dates, so far as the year is concerned, used together. Thus, 
Charles Lis said to have been beheaded in 1648-9. His 
execution had occurred between the 1st of January and 
the 25th of March. Hence, according to Old Style, it was 
in 1648 ; and, according to New Style, in 1649* 



EXERCISES. 

Our subject refers to the Heavens only as they are connected 
with the Earth. We have therefore said little of the Planets. 
But we send our students forth to study the Stars. They must 
understand which are the principal constellations and the bright- 
est stars, in order to be able to locate those circles of the Earth 
and Heavens, without which the Earth's position in regard to the 
Sun cannot be known. In thus watching the Heavens, we can- 
not but desire to understand the motions of the Planets, the 
brightest and most peculiar of the Stars. 

In what part of the Heavens are we to look for the Planets ? 
A young lady once inquired of a gentleman whether Vega, in 
Lyra,* the most magnificent star of the northern hemisphere, was 
a Planet. Some would say she should have known the difference* 
because the Fixed Stars twinkle, and the Planets do not. But to 
some eyes, the Planets rather than the Fixed Stars appear to 
twinkle. But from the place of Lyra we think no student of ours 
would have asked so mistaken a question. The Planets — we 
6peak not now of the Asteroids, the largest of which is not 
larger than a fixed star of the 5th magnitude, and the smaller 
are merely telescopic stars ; their orbits extend several degrees 
beyond the Zodiac ; — but the Planets, so interesting to our view, 
are never seen but in the Zodiac, which extends about 8° on each 
side of the Ecliptic. To Lyra we have given particular attention, 
as the directing star to point out the Winter Colure, 5° to the 
west ; and the Pole of the Ecliptic, which is on that Colure, close 
to the star a Draconis, and 25° north of Lyra. The Winter Co- 
lure is on one account the most remarkable of great circles. The 
permanent connection of the two Systems of the Earth and Heav- 
ens exists in the coincidence of this Secondary of the Equator with 

* Commonly called Lyra. Sir W. Herschel discovered this to be a doable- 
double star — four stars seen as one. 

16. What causes of confusion arose ? Why was Charles I. said 
to have been beheaded in 1648-9 ? 

20* 



234: THE SHEPHERD OF THE STABS. 

a Secondary of the Ecliptic ; and while these parts of the two 
Systems coincide, no other Secondaries in the two Systems can 
coincide. So in the connection of the Observer's System with the 
other two, if the axes of the three Systems shall ever be in the 
same plane, it must be the plane of the Solstitial Colure, and the 
three Poles above the Horizon must be in the Winter Colure. 
Let us suppose, then, that the Winter Colure is in our Meridian at 
the Summer Midnight. Then in the Meridian in its northern half, 
including the Zenith, are the upper Poles of the three Systems, 
and in no other circle but the Winter Colure, could this be the 
case.* Then the lowest point of the Ecliptic is due south, since 
its Pole is on the Meridian, and as far south of the Equator as its 
Pole is of the Earth's, that is, 23-J- degrees. But Lyra is 25° south 
of the Ecliptic Pole, that is, 65° north of the Ecliptic itself. But 
the 8° of the northern half of the Zodiac must be subtracted from 
this to find how near to Lyra a bright Planet might possibly 
come, and we find it to be 59 degrees. But the greatest northern 
declination of a Planet which might be observed, when, on a win- 
ter midnight, the Summer Colure was in the Meridian, is 23-£°+ 
8°=31-J . But Lyra's declination is about 48J°, which is 11° 
north of the possible place of any brilliant planet. But the young 
lady who asked the question, with so plain a star as Lyra to guide 
her to the place of the Ecliptic Pole and the lowest point of the 
Ecliptic, was out the way sixty degrees save one. 

If the Planets are watched on consecutive evenings, in connec- 
tion with the Fixed Stars, their annual movements will appear 
singular and confused, and their apparent sizes sometimes greater 
and sometimes less ; and any Shepherd of the Stars, as the ear- 
liest astronomers were called, who, like us, gazed at them without 
the aid of instruments, will soon conclude that these are peculiar 
bodies, having motions different from other stars. Sometimes 
they appear to advance from west to east in the order of the 
signs, their motions being then direct. Sometimes, for a suc- 
cession of nights, they appear to stand still, not moving at all with 
respect to the Fixed Stars ; they are then stationary. And some- 
times they move westward, contrary to the order of the signs, 
when they are said to retrograde. 

To show the causes of this seeming confusion, we produce a 
simple diagram. The orbit of one of the inferior Planets, of which 
there are only Mercury and Venus, is here represented by the 
circle a b c n. They are never seen far from the Sun, since their 
orbits are within that of the Earth. They have two conjunctions 
with the Sun, but no opposition, and no quadrature. In the fig- 
ure, if we suppose the Planet at a, it would be in its superior or 
upper conjunction ; when at o, in its inferior or lower conjunction. 

From the eye of an Observer on the Earth, tangents to the orbit 
are drawn to the celestial Sphere, of which a section of 60° is 

* See Figure 26. 



AN INFERIOR PLANET'S MOTION. 



sas 



taken, passing from the Sign Aries through Taurus to Gemini. 
Suppose the Observer to see the Planet, it being at b in the 
Heavens, in the first of Aries. While it is passing in its orbit from 
B, one of the stationary points, through a, its superior conjunction, 
to j>, the other stationary point, it is seen by the Observer to 



Fig. 34. 




move in the Heavens direct from Aries, through Taurus to Gemini. 
Then apparently being stationary for a time, the Observer will 
see it — while in its orbit it moves from d through c, its inferior 
conjunction, to b — apparently to have turned its course in the 
Heavens, and gone backward in the Ecliptic from Gemini 
through Taurus to Aries. It appears stationary at the Observer's 
two side-views of its orbit at b and i>, where the circle of the or- 
bit nearly coincides with the two tangents n l and s m. Suppose 
the Planet were moving on the tangent s m from d towards the eye, 
it is evident that it would not change its place in the Heavens, 
but as it approached it would become apparently larger. So when 
it was receding along the tangent n l at b, it would not change 
its place in the Heavens, but its apparent size would diminish. 
If, when it is passing through a, its superior conjunction, it falls into 
the line of the Nodes, there will be an occultation of the Planet, 



236 THE MAGNIFICENT SCIENCE. 

or a hiding behind the body of the Sun ; but if it is in conjunc- 
tion at o, the inferior conjunction, then it will transit from east 
to west, like a black round spot across the Sun's disk. The infe- 
rior Planets, when viewed through the telescope, exhibit all the 
phases of the Moon, being crescent near the inferior, and full at the 
superior conjunction. Their apparent motions are most rapid when 
nearest the eye, that is, at the inferior conjunction, 

The Superior Planets would, if the Earth were at rest, con- 
stantly move round the Ecliptic in the order of the Signs ; slower 
and apparently of less magnitude when in conjunction with the 
Sun, because then farthest from the Earth ; but faster and ap- 
parently larger, because nearer when in opposition. But the 
Earth mean time is moving, and sometimes faster than the supe- 
rior planet ; and sometimes, as the inferior planets to her, in a 
direction opposite to theirs. Owing to these causes, the Superior 
Planets have their stationary and retrograde appearances. They 
may be occulted^ or hid by the body of the Sun, but they never 
transit across his disk. 

Next to Venus, the most brilliant of the Planets, when seen by 
the naked eye, are Jupiter, Mars, and Mercury. Mars is distin- 
guished by his color, as of fiery red ; whereas the light of Jupi- 
ter, like that of Venus, is uncolored and brilliant. Seen through 
the telescope, Jupiter exhibits dark belts, supposed to be clouds. 
But when viewed through the telescope, Saturn, with his moons 
and rings, is the most interesting and curious of the Planets. 
Note.— Fig. 24 should be drawn on the blackboard, and explained. 



CHAPTER XXIII. 

Astronomy doubly honors Goo, in reference both to Material 
Objects and to Mind. — Derivation of the Term.— Nature of 
Mind, the Instrument and the Recipient. — History of 
Astronomy. — Nations who first cultivated the Science. — • 
Chinese, Indians, Chaldeans, Phenicians, Egyptian Priests, 
Greeks. — Ionian School. — Thales, Anaxamander, Anaxago- 
ras. — School of Crotona, Pythagoras, Damo, Philolaus.— 
School of Alexandria. — Arystillus, Timocharis, Aristarchus, 
Euclid, Archimedes, Eratosthenes, Hipparchus. 

1. Astronomy is the most magnificent of sciences. It 
doubly honors God, by showing man the distant wonders 
of the visible Creation, and by affording him the occasion 

Chapter XXIII. — 1. Why does Astronomy doubly honor God & 



MIND NOBLER THAN MATTES. 237 

of the highest development of that inner region of Mind, 
equally the work of God, and not less sublime than the 
starry Heavens. Astronomy is the result of Mind opera- 
ting on Stars, and Worlds, and learning the laws which 
guide them. The term Astronomy is from two Greek 
words signifying a Star and a Law.* But the human 
Science of the Stars can advance only by the efforts of the 
Human Mind. Let us, then, for a moment turn our atten- 
tion to the Mind — that wonderful Instrument which makes 
the Science it cultivates, and that great Recipient which is 
cultivated by the Science it makes. 

2. On the 11th of December, 1830, the author heard, 
at the College of France, a Lecture from Cuivier, and at 
the time thus wrote her impressions on the sublimity of a 
great Mind, as compared to the grandest of material ob- 
jects : " His large and strongly marked head is to me 
sublime. I regarded it with attentive observation, and 
considered how the works of God exceed those of man. 
Within the little circle of that wall of bone, what stores 
of knowledge reside ! The Mind which there inhabits, has 
been nourished to its prodigious growth by the products 
of the whole earth; and it has sent forth an impulse 
which every part of the civilized world has felt. Suppose 
for a moment the whole knowledge of events and facts, 
and all the reasonings and deductions, past and present, 
of that mind, were developed in words, the world could 
scarce contain the books that would be written. Suppose 
every conception of things external, whether of the con- 
cave Heavens or of the broad Earth, with her mountains 
and vales, which those eyes have conveyed to that mind, 
could be brought forth and stamped on some material 
medium, in the size which it has conceived or now con- 
ceives them, — with all the mingled forms into which fancy 
has arranged them, and all the images which other minds 

* Our title — Astronography — if supposed to have a Greek derivation, would 
he from Karpov and ypa<po, signifying to describe the Stars. We prefer regard- 
ing it as but a shorter sound for Astronomy and Geography, thus united, as in 
this work. 

1. How is Astronomy connected with the Human Mind? — 2. 
Give an example of thoughts suggested on beholding the head of 
a great man ? 



238 SIGHT— IMAGINATION — REASON- 

have furnished to that skull of a span's diameter ; if the 
channels of the deep were dry, the mighty cavities could 
not contain the pictures."* 

3. Thus Planets and Suns are not more grand or won- 
derful than the Mind which has measured their sizes and 
their distances, and comprehended the Laws of their mo- 
tion. Man, by Astronomy, cultivates both his noble Fac- 
ulty of Sight, and his nobler Imagination, that inner 
sight of the mind ; and as Reason accompanies his re- 
searches, what he sees in the Sun, the Planets, and the 
more distant Stars, comes to his mind with the equal im- 
pression of reality, whether beheld by the outer or the 
inner eye ; and this grand imagery, thus received, remains 
aglorious region of the Astronomer's Mind. . . . What 
is the history of this sublime Science ? . . . What are 
the nations, and who are the men, to whom we are most 
indebted for its cultivation ? 

4. When we look back into remote antiquity, we are 
met by facts which would seem to show that there was 
once an anterior civilization in the nations of the East, of 
which fragments alone have been preserved in the au- 
thorities on whom we depend for historical information. 
Chinese historians assert that with Fohi, contemporary with 
Noah (and some suppose identicalf ), began, in China, the 
studies both of Astronomy and Mathematics, and that 

* See Willard's Journal and Letters from France and Great 
Britain, page 120 — published in 1833, in aid of female education 
in Greece. 

f Fohi was said to have been the son of a rainbow, which is 
regarded as one proof that he was either Noah or one of his sons. 
China is now attracting more attention than heretofore, and is be- 
coming better known; and this added knowledge gives confi- 
dence to the statements of their National Historians. It does not 
appear that the Chinese make any pretensions to an absolutely- 
veracious History which goes higher than Hoan-ti. They regard 
that more ancient as mixed with fable, like the early records 
of all ancient nations. But subsequently an excellent method 
prevailed of keeping the annals of the Kingdom, which is thus 

3. What special faculties of the mind are cultivated by Astron- 
omy, and what does the Astronomer's mind retain ? — 4. What is 
asserted by Chinese Historians concerning the beginning of the 
great sciences^of Astronomy and Mathematics ? 



EARLIEST HISTOEY OF ASTRONOMY. 239 

both had so far advanced, that in the reign of Hoan-ti, 
who lived in the time of Abraham or earlier, his minis- 
ter, Fanar, made a System of Mathematical Chronology, 
founded on Astronomical Observations. He adopted, in- 
stead of our Century of 100 years, the Period, or Cycle 
of 60 years. An Eclipse is described, and is claimed to 
have been calculated, 2155 years B. C. The books of 
Confucius, published about 500 years B» C, contain pre- 
dictions of 36 Eclipses of the Sun. The Jesuit Gaubil 
relates that he examined them, and found among them 
only two false and two doubtful. 

5. By the Emperor Yu or Ju, who was contemporary 
with Confucius, the great Philosopher and Lawgiver of 
China, was founded an Observatory, which he caused to 
be attached to the wail of his capital, rising above and 
resting upon it in the form of a square tower. Here it is 
said he placed an Armillary Sphere* of six feet diameter, 
and a Celestial Globe equally large, having the Stars 

described by Clerc, a reliable French writer of the last century : 
" De tout, temps il y a eu a la Chine, le Tribunal de Mathematique 
et le Tribunal d'Histoire reunis : ces deux Tribunaux ont con- 
tinue d'annees en annees, Tun ses memoires, l'autre ses observa- 
tions pour la suite et la verification des faits contenus dans les 
cent-vingt volumes des grandes Annales. Ces Annales ont tou- 
jours ete redigees avec le plus grand soin, et l'exactitude la plus 
scrupuleuse." 

* " The Armillary Sphere is an artificial sphere composed of a 
number of circles of the Mundane Sphere (Sphere of the Earth), 
put together in their natural order, to assist in giving a just con- 
ception of the constitution of the Heavens, and the motions of 
the celestial bodies." This artificial sphere revolves upon its axis 
within a horizon divided into degrees, and movable every way 
upon a brass supporter. By the axis and circles constituting an 
Armillary Sphere, as they appear in the drawings formerly 
placed in books of Astronomy, we are reminded of our figure, 

4. What Cycle, or period of time, was introduced by Fanar ? 
In whose reign, and at about what time did this reckoning com- 
mence ? How does it appear that the Chinese calculated Eclipses 
at an early period ? — 5. Who was Confucius ? In whose reign 
did he flourish ? What was done concerning Astronomy by this 
Emperor in regard to a building ? What two pieces of apparatus 
are said to have been placed within it? What is an Armillary 
Sphere ?— {See Note.) 



240 CHINESE CHALDEANS EGYPTIANS* 

marked upon it in their natural positions. But if this 
was so, then the Chinese knowledge of Astronomy must 
have been greatly in advance of that of Geography ; for 
they held that China was the middle of the Earth — their 
name, Chang-qua, signifying the Kingdom of the Centre — 
and they supposed it to be not only the middle of the 
solid land of the Earth, but nearly the whole of it, the 
remainder being only small scraps, of which they reckoned 
72, ranged around like small islands, or as satellites which 
accompanied and decorated their own " Celestial Em- 
pire."* 

6. India, as well as China, claims great antiquity in re- 
gard to Astronomy. . . In Egypt, the priests, those dark 
and fearful men, knew perhaps more than any other 
Astronomers of ancient times concerning the heavenly 
bodies ; but the exact extent of their knowledge can never 
be known, since they cultivated Science not to enlighten, 
but to subjugate mankind ; and hence they made it occult 
and mysterious, to be taught only to the initiated, and un- 
der the seal of secrecy. . . . The Shepherds of Chaldea 
and the Mariners of Phenicia early watched the Stars, 
and formed their Observations into Systems. When Alex- 
ander the Great invaded those regions, he brought from 
Babylon to Greece the recorded Observations which 
their Astronomers had been making for 1900 years. They 
predicted (720 years B. C.) Eclipses of the Moon. Their 
predictions were not made, however, on the unerring prin- 

showing the combination of our three Spherical Systems ; but we 
think the former are less perspicuous and suggestive. We hope 
our three Systems will soon be exhibited by apparatus, where 
their connections and possible motions may be seen, and the 
whole be adjusted to show desired particular cases. 
* See Clerc's Histoire Chinoise, p. 12. 

5. What comparison may be made between Chinese Astron- 
omy and Geography ? What were their impressions concerning 
the habitable Earth ? — 6. What other nation claims great antiqui- 
ty in regard to Astronomy? What is said of the Egyptian 
Priests, in regard to Astronomy ? In what countries did the 
Shepherds and the Mariners, in very early times, begin their sci- 
entific observations of the Stars ? When and by whom was the 
Astronomical learning of eastern nations brought to Greece ? 



GREEK ASTRONOMERS. 241 

ciples since discovered and now in use ; but on long-con- 
tinued and recorded observations of the time intervening 
between Eclipses of a similar kind. By these they learned 
the actual period, which occurred between the Moon being 
in a similar position with regard to the Sun. The years 
which intervene between two of these periods are a Lunar 
Cycle. The Cycle in use with the Chaldeans they called 
the Sa?-os. It consisted of 223 lunations, or 18 years and 
10 days. Subsequently the Metonic Cycle of 19 years, 
so called from its author, Meton, was used by the Greeks. 
7. The beginnings of Astronomy come to us through 
the Greeks. The first great men of Greece who cultivated 
the Science, went to Egypt and studied with the priests. 
The earliest of these, whose name has come down to us, 
was Thales of Miletus, who, after spending his youth in 
Egypt, returned to Greece and founded the Ionian 
School. " He maintained that the Stars were of the 
same substance as the Earth; that the Moon borrowed 
her light from the Sun ; that the Eclipses of the Moon 
were occasioned by her immersion into the Earth's Shad- 
ow ; that the Earth was round ; that it was divided into 
five Zones by the Polar Circles, the Tropics, and the Equa- 
tor ; and that the Equinoctial Line was cut obliquely by 
the Ecliptic, and perpendicularly by the Meridian. By 
means of the instruction which he received in Egypt, 
Thales predicted an Eclipse of the Sun, and the fulfilment 
of this prediction raised him to a high place among his 
countrymen."* Although this philosopher taught so 
many truths, yet they were mingled with many errors. It 

* Edinburgh Encyclopedia. If Thales taught all these things, 
he must have made some fortunate guesses; for surely Sci- 
ence was not in a state of sufficient advancement that they could 
all be known. There is discrepancy among authors as to what 
these very ancient philosophers did teach, 

7. From whom do we obtain the beginnings of Astronomical 
knowledge ? Where did the first great men of Greece, who cul- 
tivated Astronomy go ? Who was the first emiment Astronomer of 
Greece? What celebrated School did he establish? What doc- 
trines is Thales said to have maintained ? What gave him a high 
place among his countrymen ? 

21 



242 THE IOKIAN SCHOOL. 

shows how little was then known of Mathematics, that it 
was considered a wonderful achievement which the priests 
had taught him to perform, that he could decide the 
height of the pyramids by the length of their shadows. 

8. Anaximander, also of Miletus, the pupil of Thales, 
succeeded him as chief of the Ionian School. He re- 
garded water as that element, from which every thing else 
was made. Filled with all the enthusiasm for Astronomy 
which the noble Science is calculated to inspire, he boldly 
taught that the Planets were analogous to the Earth, and 
were peopled with beings of a similar nature ; and he sub- 
limely conjectured that the " fixed stars were centres of 
other systems more glorious than our own? 

9. Anaxagoras, of Clazomene, a later chief of the 
Ionian schools, was so devoted to Astronomy, that he 
gave up the affairs of life, maintaining that the contem- 
plation of the stars was the natural destiny of man. A 
meteoric stone having fallen into the river Egos, in Thrace, 
his mind was greatly excited, and he produced the idea, 
then original, that the large mass composing this stone 
was a body which was revolving around the Earth lower 
than the Moon ; and since the matter which composed it 
was similar to that of the Earth, he hence concluded that 
the heavenly bodies generally were formed of the same 
materials as the Earth. Some of the solid stony bodies re- 
volving around the Earth he believed were made to glow 
by the fiery ether around them; while some, nearer the 
Earth, remained dark. These, he supposed, sometimes 
eclipsed the Moon, and sometimes, like the one at Egos Po- 
tamus, they fell to the Earth. The phenomena of the Heavens 
he attributed to the agency of fire. The Sun he regarded 



7. "What was done by Thales in a Mathematical way? What 
inference may we make from this being considered a great achieve- 
ment ? — 8. Who was the successor of Thales in the Ionian School ? 
How did he regard water ? What did he teach concerning the 
Planets ? To what conjecture is it said his thoughts reached con- 
cerning the Fixed Stars ? — 9. Who was it that maintained that the 
study of the stars was the natural destiny of man ? What event 
excited his mind ? What idea concerning this remarkable aero- 
lite, originated with Anaxagoras ? 



THE SCHOOL OF CROTONA. 243 

as a great inflamed stone ; but the Moon he supposed to 
contain hills and valleys, and to be inhabited. He was 
the first Greek to write respecting the Moon's phases and 
eclipses. The Athenians, for this, accused Anaxagoras 
of rashly intermeddling with the affairs of the gods ; and 
it was with difficulty that his friend Pericles saved him 
from perishing by their fanatical fury, and prevailed with 
them, to change his sentence from death to banishment. 

10. We come now to speak of another Greek, whose 
name looms up amid the darkness of antiquity like some 
tall mountain on the waste. This was Pythagoras, of 
Sam os, often mentioned as " the Samian philosopher." 
Pythagoras, after having studied with Thales, travelled in 
search of knowledge through Phenicia, Chaldea, and 
India ; and then went to Egypt, and there became ac- 
quainted with all the learning of the priests. Warned 
by the fate of Anaximander, he turned from his native 
land and opened his celebrated School of Crotona, in 
Calabria, Italy. But after the manner of the priests, he 
taught only those whom he had. bound to secrecy by sol- 
emn promise, and tested by a probationary discipline of 
silence. In his school he taught, as was after his death 
revealed by one of his pupils, that the Earth is a globe, 
that she moves in her annual course around the Sun, 
while she revolves daily on her own axis. Above all, 
Pythagoras taught, for the first time, the true system of 
the world, that the Sun is in the centre, and that the 
planets, with the Earth, perform annual revolutions 
around him. This is the true system, and the same 



9. What visionary and fanciful ideas had he, respecting the 
Sun and Stars ? What did he teach concerning the Moon ? What 
was the effect of his teaching upon the Athenians, in regard 
to their treatment of him ? — 10. What are the introductory re- 
marks of the author concerning Pythagoras ? Where did he go in 
search of knowledge ? Why, when educated and ready to begin 
teaching, did he turn from his native land ? Where did he estab- 
lish his school ? In what respect did he follow the example of 
the Egyptian priests? How were his teachings finally made 
public f What did he teach respecting the Earth ? What, how- 
ever, was the most remarkable of his doctrines \ 



24:4 PYTHAGORAS. 

which, after 2000 years, was revived by Copernicus. But 
what with Pythagoras, was only sublime and reasonable 
conjecture, modern philosophy, working by Mathematics, 
has made a glorious certainty. The degree of advance- 
ment in Mathematics necessary for this had not then 
been attained ; although Pythagoras was the greatest 
mathematician of his time. The demonstration of the 
beautiful theorem in Geometry* which bears his name, 
was then regarded a proud advancement in that science, 
although now standing but as its initial point. 

11. Pythagoras was so wrought into the study of the 
Heavens, that his imagination became over-excited. Hav- 
ing a great love of music, and not knowing the causes of 
the planetary motions, he fancied that there were different 
concentric solid spheres, in each of which, one of the 
planets was fixed ; and as they moved one upon another, 
they emitted harmonious sounds, although the human 
ear was, in general, too gross to enjoy the ravishing de- 
light of " the music of the Spheres." Pythagoras left his 
secret doctrines to the keeping of his learned daughter 
Damo ; but his pupil, Philolaus, after his decease, 450 
b. c, made them public. Neither Plato nor Aristotle,]- 
though so great in philosophy, did much, either for Math- 
ematics or Astronomy, — and our attention will next be 
called to the great school of Alexandria. 

12. The conquests of Alexander the Great so dazzle 

* Pythagorean theorem is the 47th of the First Book of 
Euclid. 

f Often called " the Stagyrite," because he was born in Stagyra, 
in Macedonia. 

10. What is said of the system taught by Pythagoras ? Why 
was it impossible that Pythagoras should then have made his 
system as certain as it has since been made by modern philoso- 
phy ? What is said of Pythagoras in regard to mathematics ? — 
11. How was it with this great philosopher in regard to imagi- 
nation and a love of music ? What are some of the fanciful the- 
ories framed to account for the motions of the planets ? Who 
was the chosen depositary of the secret doctrines of Pythagoras ? 
When and by whom were they revealed ? What great philoso- 
phers of Greece followed, to whom Astronomy, however, is not 
much indebted ? 



GREAT ADVANCE IN ASTRONOMY. 245 

us as military achievements, that we are apt to forget 
their more important scientific advantages* Alexander 
was the pupil of Aristotle, and his soul was imbued both 
with the love of knowledge, and with friendship for his 
great master ; and he took those to accompany him in 
his expeditions, whose special duty it was, to make obser- 
vations on various subjects, and report them to the public— 
and especially to Aristotle, who taught them orally, and 
embodied them in his works. Vast unknown countries, 
with their productions, were now brought to the knowl- 
edge of the Greeks. Thus, a new fountain of information, 
exciting to thought and effort, was opened to the world ; 
and it was continued by the connections of trade and so- 
cial intercourse with the newly discovered nations. 

13. After Alexander's death, one of his generals, Ptol- 
emy, who shared his leader's zeal for knowledge, suc- 
ceeded to the sovereignty of Egypt. He began — and his 
sons continued — to collect the most learned men and the 
best writings of the world ; and thus to lay the founda- 
tion of the great Library and School of Alexandria, 
which, for several centuries, remained as the greatest sci- 
entific light of the world. When we compare this school 
with the Ionian, we find a great advance in exactness of 
knowledge, and less of the false and fanciful. Euclid 
belonged to the Alexandrian school, and Archimedes 
was connected with it. These two men laid the founda- 
tion of those principles of geometric mensuration by which 
Astronomy at length ceased to be a conjectural, and be- 
came a certain science. Humboldt, in his Cosmos,* says, 
" during the epoch of the Ptolemies, splendid progress 

* Cosmoe, a Greek word, signifying world or universe. Some- 
times used as synonymous with universal nature. 

12. What is here said of the conquests of Alexander the Great ? 
Of what importance to science was, in this case, the teaching of a 
great master to his pupil ? — 13. What occurred after Alexan- 
der's death in Egypt, especially at Alexandria ? How does the 
Alexandrian school compare with the Ionian ? What two men 
are first mentioned, and what is said of them and the effects of 
their labors in Astronomy ? What says Humboldt of the epoch 
of the Ptolemies ? 

21* 



246 ALEXANDRIAN SCHOOL. 

was made in the scientific knowledge of the Heavens." 
Arystillus and Timocharis determined and described 
the places of the Fixed Stars. Aristarchus, of Samos, 
who was conversant with the Pythagorean views, was the 
first to recognize^the immeasurable distance of the Fixed 
Stars from our own Planetary System. He conjectured 
the twofold motion of the Earth upon its axis and around 
the Sun. Erythea, a century afterwards, endeavored 
fully to establish the hypothesis of Pythagoras, but in 
that age it met with little attention. 

14. But Hipparchus was the great luminary of the Al- 
exandrian school. He was both the founder of scientific 
Astronomy and the greatest astronomical observer of an- 
tiquity. He collected in tables all the descriptions that 
could be found from the previous records of iVstronomy ; 
and from observation of the Stars at the time of the Equi- 
noxes ; and from learning what their position at the time 
of equal days and nights had formerly been, he discov- 
ered the Precession of the Equinoxes, and the corres- 
pondent retrocession of the Equinoctial Points. A pe- 
culiar feature in the labors of Hipparchus was the use he 
made of his observations of celestial phenomena for the 
determination of geographical positions. 

Eratosthenes, of this school, who preceded Hippar- 
chus, was the most celebrated of the Alexandrian librari- 
ans. He availed himself of the materials at his command 
to compose a System of Universal Geography. He taught 
the great problem of the equal level of the whole external 
sea, surrounding all continents. Eratosthenes caused a 
degree of the Earth's surface between Syene and Alexan- 
dria to be measured, thus seeking to find an element by 
which he might approximate to the real size of the Earth. 
He made a map, which, after his decease, Hipparchus 

13. Who first determined and described the places of the 
Fixed Stars? Who first recognized their immeasurable dis- 
tance ? — 14. But who was the great astronomical luminary of the 
Alexandrian School ? What is said of him and his labors and 
discoveries ? What was peculiar respecting his teaching? What 
great geographer preceded Hipparchus at Alexandria? What 
was done and taught by him ? • - 



SLOW ADVANCE OF GEOGKAPHY. 247 

crossed with lines of latitude and longitude. These were 
the beginnings of the science of Geography, which, in the 
next centuiy, was cultivated by Strabo, a native of Pon- 
tus. But at this period, and for centuries afterwards, the 
boundaries of the eastern continent had not been ascer- 
tained ; and what dangers might be hidden in unknown 
regions, none could tell. As for Astronomy, although it 
was in advance of Geography, still no progress had been 
made in knowledge of the absolute size, form, mass, and 
physical character of the heavenly bodies. 



EXERCISES. 

We expect your interest in the examination of the starry 
Heavens will be increased, as you read of the great men of an- 
tiquity who have gazed with so much pleasure and profit upon 
the same stars, which are standing now essentially in the same 
position with regard to each other as then. The Moon was 
walking through the same bright path, then, as now. There 
were then nine staes which were noted as marking her monthly 
course, and the mariner now watches for the same stars, as did 
the mariners of old. These nine stars, which thus mark the 
track of the Moon, are Arietus, Aldebaran, Pollux, Regulus, Spies 
Virginis, Antares, Altair, Fomalhaut, and Markab. Learn them, 
as you are able, with their Declinations and Right Ascensions. 
But take one star at a time, and let that be well considered, as 
to its appearance and position, before you attempt to learn 
others. 

Let your star for study this evening be Spica Virginis. Bur- 
ritt, in his excellent work, " The Geography of the Heavens," 
thus describes its position. M Spica Virginis, in the ear of corn 
which the Virgin holds in her left hand, is the most brilliant star 
in the constellation Virgo, and is situated nearly 15° E. IS". E. of 
Algorab in Corvus, about 35° S. E. of Denebola, and nearly 
as far S. S. W. of Arcturus — three very brilliant stars of similar 
magnitude that form a large equilateral triangle pointing to the 
South. Arcturus and Denebola are also the base of a similar 
triangle on the North, terminating in Cor Caroli, which, joined to 
the former, constitutes the Diamond of Virgo. The length of 

14. How were his labors extended by Hipparchus? What 
geographer afterwards appeared? What, however, was the 
state both of geographical and astronomical knowledge ? 



248 THE BRIGHT STAR OF VIRGO. 

this figure, from Cor Caroli on the North to Spica Virginis on 
the South, is 50°. Its breadth, or shorter diameter, extending 
from Arcturus on the East to Denebola on the "West, is 35^°. 
Spica may otherwise be known by its solitary splendor, there 
being no visible star near it except one of the 4th magnitude, 
situated about 1° below it on the left," When you have identi- 
fied the star, then proceed to judge concerning its Right Ascen- 
sion and Declination, and finally consult the Globe or a Table 
of Right Ascension, in order to correct your judgment. 

When you look at Spica Virginis, think of Hipparchus, who 
discovered (b. c. 180) the Retrocession of the Equinoctial Points, 
in part by comparing the position of this star as he saw it, with 
what had been, as he learned, its former situation ; and also 
consider that the accurate description made by him, and after- 
wards renewed by Ptolemy and others, has put it in the power 
of later astronomers to decide exactly the time (50") of the Pre- 
cession of the Equinoxes, and the space (about one-third of a 
degree) of the Retrocession of the Equinoctial Points. 

Find on the Terrestrial Globe, China, India, Chaldea (its capi- 
tal ancient Babylon), and Egypt. Describe the position of 
Greece and of Athens, the seat of the Ionian School ; of Samos, 
the birthplace of Pythagoras ; of Crotona (in Italy), where Py- 
thagoras kept his famous school ; of Alexandria, in Egypt, where 
was the greatest Library and the greatest School of ancient time, 
where Eratosthenes taught Geography, Euclid Geometry, and 
where Hipparchus laid the foundation of scientific Astronomy. 



CHAPTER XXIV. 

History of Astronomy after Christ. — Ptolemy — His System. — 
The Almagest. — Historical Great Events quicken Inventive 
Genius. — Discovery of America. — Copernicus — His System : — 
Compared with Ptolemy's. -Tycho Brahe. -Kepler — His three 
Laws. — The Discovery of the Telescope. — Galileo — His Per- 
secution. HUYGENS AND OTHERS. SlR ISAAC IS~EWTON — HlS EX- 
CELLENT Character — Great Law of Universal Gravitation. 

1. Ptolemy, of the Alexandrian school, who was born 
A. d. 70, at Pelusium, in Egypt, and flourished in the 
beginning of the second century, was the most eminent 
astronomer who lived after Hipparchus, until the time of 
Copernicus. But although for so many centuries he led 
the opinions of mankind, we may now perceive that his 
mind and genius were not of the first order; for that 
seemed to him to be truth which was not truth ; but 
which, lacking simplicity and clearness, bore rather the 
mark of specious error. 

2. The system taught by Ptolemy, supposed the Earth 
to be at rest in the centre, and the Sun, Moon, Planets, 
and Fixed Stars to move around it once in twenty-four 
hours. To account for the irregular motions of the Plan- 
ets, Ptolemy, with great ingenuity, invented a machinery 
of retrograde spheres, called epicycles,* into one of which 

* Humboldt, in the Cosmos, says : " The idea of a crystalline 
vault of heaven was handed down to the Middle Ages by the 
Fathers of the Church, who believed the firmament to consist of 
from 7 to 10 glassy strata, incasing one another like the different 
coatings of an onion. This supposition still keeps its ground in 
some of the monasteries of southern Europe, where I was greatly 
surprised to hear a venerable prelate express an opinion in refer- 

Chapter XXI Y. — 1. Who was the great astronomer of the 
Middle Ages? Since Hipparchus flourished about 130 years 
before Christ, and Copernicus about 15£ centuries after, how many 
centuries elapsed without an astronomer of equal eminence ? What 
opinion may now be formed concerning the mind and genius of 
Ptolemy ? — 2. Give some account of the system of Ptolemy. 



250 PTOLEMAIC SYSTEM. 

each, planet was supposed to be fixed, each having its 
proper motion sometimes backwards, and sometimes for- 
wards. These epicycles he supposed to be mingled with 
solid spheres, one of which having power to move the 
others, he called it the prirmim mobile* Ptolemy col- 
lected the fragments of ancient Astronomy. He made an 
Artificial Celestial Globe, on which he placed the Con- 
stellations, rectifying the situation of the stars for his own 
time, and giving their differences from that of Hipparchus. 
His catalogue of the Stars — by far the most valuable of his 
works — still remains, and is the oldest extant. 

3. He was an accurate observer, an industrious collector 
of facts, and a diligent and voluminous writer. Ptolemy 
and Strabo were the greatest geographers of the period, 
and both wrote extensively on geography. Ptolemy's 
work on Astronomy was, however, his capital perform- 
ance ; and it was long regarded as the most learned work 
existing. It was divided into 13 books, and was trans- 

ence to the fall of aerolites at Aigle, which at that time formed 
a subject of considerable interest, that the bodies we called me- 
teoric stones, with vitrified crusts, were not portions of the fallen 
stone itself, but simply fragments of the crystal vault shattered 
by it in its fall. Kepler, from his considerations of comets, which 
intersect the orbits of all the planets, boasted, nearly two hundred 
and fifty years ago, that he had destroyed the 77 concentric 
spheres of the celebrated Girolamo Fracastaro, as well as all the 
more ancient retrograde epicycles." 

* When Alphonso X., king of Castile, collected at his capital 
the great astronomers of the world — who believed, with reverence 
what Ptolemy had taught, his mind revolted at such a cumbrous 
and complicated scheme of the Universe. He did not believe 
that God had made what man could see to be unwise, and he 
rebuked their blind belief somewhat too boldly by declaring that 
" if the Almighty had called him into counsel when he was about 
to create the world, he could have given him good advice." It 
was by the direction of this monarch that the Alphonsine Tables 
were undertaken, in 1252. They were corrections of the Ptole- 
maic Tables. 



2. How, in endeavoring to prop up absurdities, did he manifest 
ingenuity, if not genius ? — 3. In what respect did he manifest 
great industry, and do good service to the cause of Astronomy ? 
What other science besides Astronomy did Ptolemy cultivate ? 



THE ARABIANS. 251 

lated, a. d. TOO, into Arabic. The Arabians gave it the 
title of Almagest, or "The Great Composition," by which 
it has ever since been known. It was translated from 
Arabic into Latin ; but at the revival of letters in the fif- 
teenth century, the Greek text was found and printed. 
The work is still valuable for its minute description of the 
stars, by which the difference of their places at that time, 
at the era of Hipparchus, and at the present or any future 
period, can now be known. 

4. The Arabs, under the Caliphs, cultivated Astronomy, 
and the Caliph Al-Mamun was himself an eminent 
Astronomer. The Arabians at this period excelled other 
nations in Mathematical Science, particularly in Algebra; 
and although they received the false system of Ptolemy, 
yet they contributed to the establishment of the true, by 
observing and recording all appearances and variations in 
the places of the heavenly bodies, by which later astrono- 
mers had a greater range of data collected for their use. 
The Tartars acquired from them a taste for Astronomy, 
and Uliegh Beigh, one of the descendants of Tamerlane, 
at his capital, Samarcand, built and furnished an obser- 
vatory, collected learned men, and caused an independent 
catalogue of the stars to be drawn up, which has also 
proved serviceable to later Astronomers. 

5. The progress of the human mind in scientific dis- 
covery is sometimes led on by great historical and geo- 
graphical events. Thus, the opening of a new world to 
the ancient Greeks by the expedition of Alexander the 
Great, led the way to the Alexandrian Library and School, 
and to that scientific awakening of mankind, which took 
place in the days of Archimedes and Hipparchus. And 
thus, the opening of another and more astonishing new 
world by Columbus, was followed by a similar and still 

3. Give some account of Ptolemy's greatest work. — 4. "Who 
next to Ptolemy are mentioned as having cultivated Astronomy ? 
In what did the Arabians particularly excel ? In what respects 
were their labors serviceable to Astronomy ? "What people de- 
rived a knowledge of Astronomy from the Arabs, and what indi- 
vidual among them ? — 5. How is the human mind sometimes led 
in scientific discovery ? "What two examples are here given ? 



S52 COPERNICUS. 



• 



more remarkable awakening of the scientific energies of 
the human mind in the 15th and 16th centuries. 

6. The first of the intellectual giants who at this period 
put forth his strength upon Astronomy, was Copernicus, 
a native of Thorn, in Prussia, who was born 1473, and 
who published the result of his labors in 1530. He taught 
the true system of the universe ; that system which places 
the Sun in the centre, with the Planets, including the Earth, 
revolving around him-— the Earth and the other Planets 
performing diurnal rotations on their axes. This scheme 
was now no mere fortunate guess. Copernicus had before 
him a large amount of Astronomical knowledge in the 
recorded observations of his predecessors, with a good de- 
gree of advancement in mathematical science ; and his 
theory of the Solar System was founded on proven facts, 
and sufficient reasons. 

1. Copernicus not only manifested an intellect of the 
highest order, but he showed also a corresponding moral 
elevation. He boldly stood up against the "hoary er- 
ror" of the Almagest, and braved the displeasure of the 
priests ; for the Church was zealously attached to Ptol- 
emy's system, regarding it as proved by the evidence of 
the senses, and according w r ith the Scriptures. In oppo- 
sition to its intricate absurdities, Copernicus thus describes 
the simplicity of his own grand scheme of the Heavens. 
*' By no arrangement," he exclaims with enthusiasm, 
" have I been able to find so admirable a symmetry of 
the universe, and so harmonious a connection of orbits, as 
by placing the lamp of the world, the Sun, in the midst 
of the beautiful temple of nature, as on a kingly throne, 
ruling the whole family of circling stars that revolve around 
him." 

8. Although Pythagoras had sketched the same majes- 

6. Who was the first of the men of great genius to come for- 
ward after the discovery of America? That event happened 
1498. How old was Copernicus at that time ? How long after 
that did he publish his system f What does the Copernican sys- 
tem teach ? How was it founded ? — 1. What was the intellec- 
tual and moral character of Copernicus ? By whom was he spe- 
cially opposed ? How does he describe his own system? 



£EPLEft. 253 

tic and simple view of the Heavens, yet Copernicus did not 
borrow from him. He produced his own more perfect 
system by the original working of his own genius, upon 
far more ample materials ; and his system, unlike that of 
Pythagoras, could never have been lost ; not only because 
he taught it publicly, and committed it to writing, and by 
the then recent discovery of the art of printing copies were 
multiplied, but because it was thus produced with proofs, 
which satisfied the greatest and most logical minds. But 
Copernicus left his system encumbered with the imaginary 
and inadequate idea of those interminable solid spheres, 
in which it was supposed that the heavenly bodies must, 
since they moved, be placed. 

9. John Kepler was born in 1571, in Wiel, in the 
duchy of Wurtemburg. During the lifetime of his father, 
who was an innkeeper, his advantages for learning were 
small ; but on his death, his mother found means to for- 
ward the cultivation of his great natural abilities, by pla- 
cing him in the university of Tubingen, where he made 
such rapid advances in philosophy and mathematics, that 
Tycho Brahe, the great Danish astronomer, then much 
distinguished by Rodolphus, emperor of Austria, invited 
the young scholar to reside with him at Prague, the cap- 
ital of Bohemia, and study Astronomy, with the advan- 
tages afforded by his instruction and observatory. Tycho 
Brahe denied the great truths taught by Copernicus, and 
he read with reverence the Almagest of Ptolemy ; deny- 
ing, however, some parts of his system, and substituting 
a scheme of his own scarcely less absurd. Kepler was 
too independent in his thoughts, to make the connection 
pleasant between him and the opinionated Tycho Brahe. 

10. But notwithstanding this, Kepler was, in his future 

8. What parallel is here drawn between the Copernican and 
Pythagorean systems ? What drawback still existed to the sci- 
entific light spread by the system of Copernicus ? — 9. Give an 
account of the birth and early years of John Kepler. By whom 
and to what place was he invited from the university ? For 
what object was he invited ? Give some account of the opinions 
of Tycho Brahe. What is said of the connection of Kepler with 
Tycho Brahe ? 

22 



254 GENIUS AND PERSEVERANCE. 

astronomical course, greatly benefited by the unwearied 
celestial observations which Tycho Brahe himself made,' 
and which he imposed on Kepler, who was thus laying 
up a store of new facts and data for reasoning. When 
Tycho Brahe died, he left it to his pupil to complete the 
tables which he had begun. This Kepler did, and dedi- 
cating them to the Emperor, called them the Rodolphine 
Tables. He was made by the Emperor royal astronomer, 
but he was afterwards ill-treated by him, and left to suffer 
from poverty ; so that he removed from Prague to Lintz. 

11. But whatever was his outward fortune, Kepler ex- 
perienced within himself the stirrings of a mighty mind 
fixed on the most sublime of subjects, and by degrees 
bringing forth results which to this day astonish the sci- 
entific world ; and which, as he truly said, made " a total 
reformation in Astronomy." He had before him the new 
stock of facts derived from the mingled observations of 
Tycho and himself, and especially those resulting from the 
fixed scrutiny of years upon a single astronomical object, 
the orbit of Mars. Kepler saw that the system of Coper- 
nicus, as to the arrangement of the heavenly bodies, was 
true, but that the whole theory of solid spheres and epi- 
cycles was fabulous. But how did the planets move ? — in 
what orbits ? — and how were their seeming irregularities 
to be traced to regular laws ? 

12. Long and patiently did he investigate, and at 
length, after nineteen years of study, he brought to light 
and fully proved the three laws, designated as " the laws 
of Kepler ;" — rather they are laws of the Almighty, dis- 
covered by him. As they are now a part of the study 
of every liberally educated person, they stand arranged as 
they should be learned, but not in the order of discovery, 
for Kepler produced the second before the first. 

10. How was Kepler benefited in his astronomical course? 
Whose work did he complete ? What had Kepler from the Empe- 
ror Kodolphus ? — 11. But what may be said of the inner scientific 
life of Kepler ? And what of the results produced by the working 
of his mind ? What materials had he to work upon ? How did 
he regard astronomy as left by Copernicus ? — 12. What is said of 
the time and manner in which Kepler produced his three laws ? 
In strictness, are they laws of Kepler ? 



GALILEO. 255 

13. Kepler's three laws, as found in books of science, 
are, first, The orbits of the Planets are not circular, but 
elliptical, having the Sun in one of the foci. The second 
in place, but the first discovered, Kepler wrought out after 
observing that Mars moved with a rapidity proportionate 
to his distance from the Sun ; and after inventing the fan- 
cied medium of measurement, which is called the radius 
vector, he enunciated the law that the radius vector, as 
the body revolves, describes on the plane of its orbit 
equal areas in equal times. Last, he discovered his third 
law, that in the revolutions of the planets and their satel- 
lites the squares of the times of their periodic revolutions 
are as the cubes of their distances. These laws prove 
that the Maker of all worlds is the Infinite Geometer — 
the Perfect Mathematician. 

14. This third discovery was Kepler's crowning achieve- 
ment. The thought occurred to him on the 8th of March, 
1618. The elements by which he was to decide were 
before him. He proceeded to calculate, but at first made 
a mistake ; — the result disappointed him, and he aban- 
doned his principle. But on the 15th of May he rallied 
to a fresh attempt, again made the calculation, succeeded 
in bringing out the result required, and the great principle 
was forever established.* 

15. Hitherto the study of the Heavens had been pur- 
sued by astronomers solely by the unassisted sense of 
sight ; but a great change was now in progress. Contem- 
porary with Kepler was Galileo, the great astronomer of 
Italy (born in Florence, 1564) ; who, although not abso- 

* See Note in " Cosmos/' p. 695. 

13. What is set down in ordinary books as the first of the three 
laws ? What is reckoned as the second ? And what is the third 
and greatest of these laws ? When we find the great works of 
God made according to the most abstruse rules of mathematics, 
what must we conclude ? — 14. Give the time and circumstances 
of Kepler's final solution of the great problem of the relations 
between the times and distances of the planets. — 15. Up to this 
period how had astronomers pursued their studies and observa- 
tions ? By what instrument was a great change effected ? What 
is the country of Galileo, and the date of his birth ? 



256 THE TELESCOPE. 

lutely the inventor of the Telescope, has the honor of 
being the first who adapted and applied it to astronomi- 
cal purposes. There were, at the beginning of the 
16th century, simultaneous improvements made in eye- 
glasses ; and two Germans, working separately, came to 
the knowledge that they might be so arranged as to mag- 
nify distant objects, and bring them to an apparent near 
view. This was the principle of the telescope. This dis- 
covery was made in 1607, by Hans Leppershey, a native 
of Wesel, in Germany, and about the same time by Jacob 
Adriansz. The double microscope was invented a little 
earlier, by Zacharias Jansen. Both Leppershey and 
Jansen were spectacle-makers of Middleburg. 

16. Galileo heard of their discoveries in 1609, and con- 
jecturing what must be the essential points of a telescope, 
he being at Padua, constructed one for his own use, and 
there, for the first time, the magnified Heavens were viewed 
by man. By the extension of the powers of his vision, 
Galileo at once made important discoveries. The Moon's 
surface, as showing its variant shadows of mountains 
thrown opposite to the light, and its darker valleys 
receding from it, was thus seen by him to be opake, like 
the Earth. Numbers of fixed stars, which had never before 
been seen, now met the gaze of the delighted astronomer, 
in whatever direction he turned his telescope. When it 
was directed to the Milky Way, he saw so many stars 
that he conjectured its whiteness to be — what Sir William 
Herschel afterwards demonstrated — but the blended light 
of myriads of distant stars. When he examined the 
Planets, new wonders appeared. Venus, as Copernicus 
had asserted, waxed and waned, like the Moon. Jupiter, 
Galileo discovered, was not solitary, but attended by four 
satellites. He looked upon Saturn, and pronounced it 
unlike the other Planets, believing there were three bodies 



15. How far is Galileo entitled to the honor of introducing the 
telescope ? "Who were its absolute discoverers ? "Who discovered 
the microscope? — 16. Where and by whom were the magnified 
Heavens first seen ? What discoveries did Galileo immediately 
make by the use of his telescope ? 



TRUTH NEVER UNLEARNED. 257 

united. But his telescope was yet too small and imperfect 
to show with exactness its peculiar figure. 

17. By the phases of Venus, and other discoveries 
which Galileo had made by means of the telescope, he 
had proved that the system of Copernicus was inevitably 
true ; and he openly taught it as comprising the annual 
and diurnal motions of the Earth. The Inquisition, then 
in full power in Italy, regarding the new doctrine as anti- 
Christian and irreligious, forbade Galileo to teach it. To 
evade the prohibition — for he strongly felt the natural 
dread of imprisonment and torture, as well as the discov- 
erer's impulse to impart his discoveries — he wrote on the 
system of the world, in the form of a dialogue, where one 
speaker takes ground in favor of the Ptolemaic, and ano- 
ther in favor of the Copernican system. And although 
the author carefully abstained from expressing any prefer- 
ence of his own in favor of either, yet his book being 
observed by the inquisitors to make converts to the Coper- 
nican system, they issued a decree, in which they declared 
that the motion of the Earth was a doctrine " absurd, false, 
heretical, and contrary to Scripture," and they condemned 
the book, and imprisoned the author. Galileo was now 
old. An assembly of cardinals, before whom he was 
called June 22d, 1633, required him to recant his errors, 
and he knelt down before them, and, at their dictation, 
declared that he " abjured, execrated, and detested the 
absurdity, error, and heresy of the Earth's motion. 5 ' And 
even this did not so satisfy his fanatical persecutors that he 
obtained his full liberty. Some have said that he whis- 
pered, as he rose from his knees, " It moves, notwithstand- 
ing." Whether he uttered these words or not, he no 
doubt so believed ; for all mankind united cannot hinder 
the truth of God, nor make the mind which has learned 
and known — ever unlearn, or unknow it. 

17. What had Galileo proved by the use of the telescope? 
What did he teach ? What is said of the Inquisition ? What 
was now the course of Galileo ? What was its effect, and what 
was done and declared by the inquisitors ? Give an account of 
the requirements of the inquisitors, and the recantation of Galileo 
as an example of the folly and weakness of mankind. 

22* 



258 HtTYGENS, CASSINI, ETC- 

18. A host of Astronomers followed in the tram of 
Kepler and Galileo, Huygens improved the telescope, 
and by adding pendulums to clocks, he aided in the exact 
measurement of time, and led to a knowledge of the 
spheroidal form of the earth ; and he discovered that the 
singular appearance of Saturn was caused by a large ring in- 
clined 30° to the Ecliptic. He also made profound researches 
respecting central forces, which prepared the way for the 
discoveries of Newton. Dominic Cassini, professor of 
Astronomy at Bologna, Italy, discovered the diurnal revo- 
lutions of Jupiter, Mars, and Venus, He prepared tables, 
from his own observations, of the eclipses of Jupiter's sat- 
ellites, which were of great use in finding longitudes ; he 
discovered five of the satellites of Saturn, and the rotation 
round its axis of one of the number ; he observed the belts 
upon Jupiter and Saturn ; and finally, he discovered that 
Jupiter was an oblate spheroid, flattened at the poles, and 
having its equatorial diameter to its polar as 15 to 14. 

19. In England, under Charles II., the Royal Observa- 
tory was erected at Greenwich, and a succession of eminent 
astronomers was placed at its head, the first of whom w r as 
Flamstead, who explained the Equation of Time ; and the 
second was Halley, distinguished for his unwearied 
observations upon the Moon. 

20. There was still in the Science of Astronomy a void ; 
for although Kepler had embodied in his Laws the great 
facts concerning the motions of the heavenly bodies, yet 
none knew the reason why such facts existed. The man 
who supplied this void was Isaac Newton, He was 
born in Woolstrope, Lancashire, England, on the 25th of 
December, 1642. The common idea that genius creates 
opposition and leads to worldly misfortunes, seems not to 
have been a reality in the case of Newton. So sunny was 

18. Who of the Astronomers following Galileo and Kepler, is 
first named? What services to Astronomy and discoveries are 
attributed to Huygens ? What to Dominic Cassini ?— ] 9. What 
was done to encourage the Science of Astronomy in England? 
Who were the first Directors of the Royal Observatory at Green- 
wich ? — 20. Why was there still a void in Astronomical Science ? 
Who supplied this void ? Where and when was he born ? What 
is a common idea respecting genius ? 



NEWTON, 259 

his disposition, so meek and conciliating his demeanor, that 
all who knew, loved him ; and although he could not es- 
cape some disputes with the opposers of his new doctrines, 
yet, on the whole, life was to him as a pleasant voyage. 

21. Newton manifested such early spontaneous talents, 
that his mother*' gave him advantages of education which 
his moderate fortune had not entitled him to expect ; and 
he was early sent to Trinity College, Cambridge. Here 
favors and honors awaited him. After his education was 
concluded he received government patronage without his 
own solicitation — being made Master of the Mint on a liber- 
al salary. In 1703 he was elected President for life of the 
Royal Society ; and two years afterwards, he was knighted 
by Queen Anne at Trinity College. He was liberal, say- 
ing that those " who gave nothing till they died, never 
gave ;*' but he was at the same time so economical, that 
he remained not only free from pecuniary embarrassment, 
but at his death, 1727, he left to his relatives (never having 
married) a fortune of thirty-two thousand pounds. Such 
was Sir Isaac Newton— meek as the most lowly, yet pos- 
sessing that grandeur of intellect and purity of morals, 
which connect man with angelic natures. 

* It is worthy of remark, that both Kepler and Newton were, 
during childhood, under the sole charge of their mothers ; New- 
ton's father dying before his birth, and Kepler's, who had been an 
inn-keeper, dying while he was yet a child. In both cases, the 
mothers gave their highly gifted sons unexpected advantages ot 
education, without which the world would never have been thus 
benefited by their labors. They were both great Mathematical 
scholars at the University ; and without Mathematics, though 
they might have had brilliant hypotheses, they could never have 
confirmed them by proof; and Mathematics can only be attained 
by long study. Kepler had the grief, as is related in a note in 
" Cosmos" to be obliged to defend his mother in her old age, in 
those days of superstition, from a prosecution for witchcraft. 

20. What qualities did Newton possess which seemed, in his 
case, to command universal good- will? — 21. Relate some of the 
events of Newton's childhood and youth ? What is worthy of 
remark concerning the mothers of Kepler and Newton? (See 
Note.) What is related of Newton after his education was con- 
cluded? What is said of his liberality? His economy? The 
time of his death ? His character ? 



260 newton's great discovery. 

22. Astronomy, as left by Kepler, was as a statue ; New- 
ton's discovery, as the breath which gave it life. It 
is said the fall of an apple first excited his thoughts. He 
probably associated this falling fruit with that of other 
trees in every latitude — the nuts of the frigid, and the 
oranges of the torrid Zone. All fruits fall from their pa- 
rent trees in straight lines converging from all parts to- 
wards the centre of the Earth. There was then in 
Nature a law impelling the centres of bodies towards 
each other, the smaller to the greater* To this force 
he gave the name of Gravitation. He next consid- 
ered how far Gravitation extended upwards. It existed 
on the tops of the highest mountains. Why not still 
higher, even to the Moon ? Why not to all the heavenly 
Bodies ? But the philosopher soon saw, that not merely 

Quantity of Matter, but distance, must affect the law of 
rravitation, or else terrestrial objects, — even the Moon, 
would fly to the Sun, rather than remain attached to the 
Earth. At length, after years of observation, thought, and 
study, he completed his grand discovery, and announced 
to the world the great Law of Universal Gravitation — that 
the centres of all bodies are attracted towards each other, 
directly as the quantity of matter, and inversely as the 
square of their distance. 

23. The fertile mind of Newton was not confined to 
Astronomy. He made important discoveries in Optics, 
and profound advances in Mathematics. He bent the 
energies of his mind to Theology, — believed that the God 
of Nature had made a Revelation to man — and arranged a 
system of Scripture Chronology. He embodied his dis- 
courses on the various branches of Natural Philosophy 



22. Describe the beginning of the mental process of Newton, in 
discovering the universal law of gravitation ? How might the 
fall of an apple lead his thoughts ? How the consideration that 
bodies on the highest mountains gravitate towards the earth ? 
"Why might it not be supposed that all bodies gravitate merely 
according to quantity of matter \ "What is the Universal Law of 
Gravitation? — 23. What studies besides Astronomy did Newton 
pursue, and with what success ? What is the title of his great 
work? 



THE THREE SPHERICAL SYSTEMS. 



261 



in a great work, written in Latin, and entitled, " Philoso- 
phise Naturali Principia Mathematical familiarly quoted 
as "Newton's Principia." 



EXERCISES. 

We will now review our three Spherical Systems ; and then in 
idea we will add a Fourth System, as introductory to the follow- 
ing chapter. 

We will first suppose the three Systems to be connected as in 
Fig. 35. Each is here designated by a distinctive character. If, as 

Fig. 35. 

ZENITH 




~*-*-#-#-*L*-*-#- 



you study the figure, you draw on paper, increase the linear size, 
at least four times, — and twice that amount if you draw on 
a blackboard. You will then be able to make these charac- 
ters much more distinctive, and especially to show a greater 



262 THE GALACTIC SYSTEM. 

difference between the dotted and the unbroken lines, which, as 
formerly, are here taken to represent the Observer's and the 
Earth's Systems. The line of stars appropriately designates the 
System of the Heavens. The planes of three Secondaries, one of 
each System, are here made to coincide, by supposing a time 
when the Observer has, as in the night figure, the Solstitial Co- 
lure coincident with his Meridian; and in no other way could the 
Poles of the three Systems be in the same (combined) circle, 
their axes all lying in its plane. On the figure, the Secondary of 
the Ecliptic — the First of Aries and Libra — is, to prevent confu- 
sion, drawn larger than the Secondaries of the other two Sys- 
tems, which thus appear concentrically within it; but to the 
Observer, in reference to whom they are drawn, it is precisely the 
same ; — since a thousand concentric circles, drawn on the plane 
of his Meridian, would in the Heavens occupy to him the same 
place. With these observations, we believe that any pupil who 
has followed the course of our instructions, may, by beginning 
with the Observer's System, and assuming the Observer's lati- 
tude, be able to connect first his System with that of the Earth, 
and then combining with the two the Starry System of the 
Heavens, — not only construct the figure, but understand it. 

The fourth Spherical System which we wish our pupils now, in 
idea, to add, may be called the Galactic System, from its Great 
Circle, the Galaxy or Milky Way ; or rather from a circle which 
most nearly conforms to the Galaxy ; that being to appearance 
somewhat irregular, although it is supposed the greatest and 
most sublime of circles. " This circle," says Sir John Herschel, " is 
to sidereal motion what the invariable Ecliptic is to planetary 
Astronomy — a plane of ultimate ground reference — a ground- 
plane of the Sidereal System." We might name our fourth System, 
on this authority, the Sidereal System ; but we prefer the term 
Galactic, because it is not equally liable to be misunderstood. 

Knowledge to be permanent, must have its isolated facts, sys- 
tematically connected ; and it is worth while for this object, if for 
no other, to study the stars in connection with the grand scheme 
of which the twoHerschels are the authors, although we have pre- 
sumed to bring it forward as the fourth System in our peculiar 
arrangement of Astronography. According to our definitions, all 
the positions of the Galactic System, and all its intersections with 
the Systems of the Earth and Heavens, are permanent positions. 
Sir John Herschel wisely begins by first comparing this System 
with only that of the Earth. We will then examine the Celestial 
Globe, and see how the Great Circle and Poles of the Galactic 
System are situated with regard to the Equinoctial and its Poles. 
And here, as in the intersections of any two Systems, we shall find 
a Secondary of each, coinciding witli a Secondary of the other ; 
and since every Secondary of a system passes through its poles, 
this one coincident or combined circle will contain the poles of 
both, This in the intersections of the Galactic and the Earth's 



THE GALACTIC POLES. 263 

System will be such a Secondary of the former as coincides with 
the Equinoctial Colure in the latter. We shall then find the 
Poles of the Galactic System on the same circle where we began 
our study of the Heavens, and on which are the three first letters 
of our sidereal alphabet, Megrez, Cynosura, and Caph. The Galac- 
tic Poles are then on this Circle, but on what parts ? They are of 
course everywhere 90° from the great Galactic Circle, and that 
passes through Cassiopeia, we will suppose, in Caph. Then trace 
from Caph through Cynosura and Megrez, and on the Circle 30° 
south of Megrez will be the northern Galactic Pole, 60° from the 
Pole of the Earth, and 30° north of the Autumnal Equinoctial 
Point.* The southern Galactic Pole will of course be upon the 
opposite, or Vernal half of the Equinoctial Colure, as many de- 
grees South of the Equinoctial as its North Pole is North. The 
Great Circles of these two systems intersect at angles of about 
63°. We recommend to our students to study Sir John Herschel's 
description of the Milky Way, contained in his " Outlines of As- 
tronomy," looking on the Celestial Globe, but not wholly trusting 
to it, since the Galaxy is in many parts incorrectly laid down. 
Our next and last Exercise will be connected with the Terrestrial 
Globe. 



* By referring to Sir John Herschel's description of the Milky "Way, it may 
be seen that he place? the North Galactic Pole 3 degrees farther south — that 
is, having a north polar distance of 63° instead of 60°, and that he places it 
47 minutes (less than a degree) east of the Equinoctial Colure ; hut the subject 
not admitting of exactness, we have taken the liberty of using numbers nearly 
approximating to our authority, because they are so easy to remember, espe- 
cially as taken in connection with our previous instructions ; and we think it 
wise in the instructor to let his scholar first get the easy rule thoroughly into 
his memory, and afterwards learn the small exceptions. 



CHAPTER XXV. 

Astronomy as left by Kepler and Newton. — Mathematical 
Astronomy. — Optical Astronomy.— Bodies added by Discov- 
ery to the Solar System. — Aerolites. — Tremendous Shower 
at Aigle in France. — Meteoric Shower in North America, 
1833. — Terrible Appearance at Crema. — Franklin's Discov- 
ery. — Morse's Invention. — Changes in the Stars.— Appear- 
ance and Disappearance of the great Star in Cassiopeia. — • 
The two Herschels. — Sir W. Herschel's great Plan and La- 
bors in " gauging the Heavens." — Continued by Sir J. Herschel. 
■ — The Telescope. — The Discovery of the Southern Heavens. 
—Great Discoveries of Stars in the Milky Way. — Sublime 
Hypothesis of Sir W. Herschel concerning the Motion of 
the Sun. — The Milky Way the paramount Circle of the 
Heavens. 

1. Astronomy may be said to have been left by the 
labors of Kepler and Newton, a perfect science, yet only in 
the same sense in which a child may be said to be a per- 
fect human being. Development and expansion were 
needed, and they have been supplied by a host of astron- 
omers who have since flourished ; and who, while adding 
proof to certainty, concerning the laws taught by Kepler 
and Newton, have enlarged the boundaries of the science 
in various directions. The department of Mathematical 
Astronomy has been successfully pursued by La Place of 
Paris, in his great work on " Celestial Mechanics." An- 
other French astronomer, Arago, has made wonderful 
discoveries concerning light ; by means of which the dis- 
tant heavenly bodies tell the astronomer who examines 
them with the proper glasses, whether they shine by their 
own inherent light, whether it comes from a luminous 

Chapter XXV. — 1. In what sense may the science of As- 
tronomy be said to have been left perfect by Kepler and New- 
ton? What was still lacking, and how supplied? What has 
been done by La Place ? What by Arago ? 



THE TWO HEESCHELS. 265 

atmosphere, or whether it is reflected, like the moon's, 
from some luminous body. 

2. Astronomy has, since the time mentioned, been ex- 
tended by the discovery of two large planets and a num- 
ber of satellites, — by about twenty asteroids between Mars 
and Jupiter, and by a great number of comets. The large 
planet Uranus was discovered, March 13, 1781, by Sir 
William Herschel, who with his son, Sir Johx Her- 
schel, still living, are the most eminent astronomers who 
have flourished since the days of Xewton. In 1788-9, Sir 
William Herschel discovered with his colossal telescope 
the two innermost of Saturn's satellites, — the second from 
that planet performing its revolution around its primary 
in less than a day. Of the asteroids, Ceres, discovered in 
1801 by Piazzi, a Sicilian astronomer, was the first known, 
and since that period about twenty others have been dis- 
covered. Lastly, as the grand triumph of astronomy, the 
large planet Neptune was discovered before it was seen, 
by its perturbing force first pointed out by M. Bouvard, 
as exercised upon Uranus, by means of which that plan- 
et's motions in its orbit were disturbed. Le Verrier, of 
Paris, and Adams, of Cambridge, England, both announced 
the existence of a new large planet without the orbit of 
Uranus, and finally, September, 25, 1846, it was actually 
seen by Galle. 

3. Astronomers have of late paid much attention to 
Aerolites, which are the various phenomena designated 
as falling or shooting stars, fire-balls, and meteoric stones. 
Shooting or falling stars, also called meteors, when seen 
singly, are of common occurrence ; but showers of meteors, 
fire-balls, and meteoric stones are rare. For the chrono- 



2. What bodies of the Solar System have been discovered 
since the days of Newton ? By whom and when was the large 
planet Uranus discovered? What satellites were discovered 
by the same astronomer ! By whom and when was Ceres, the 
first known of the Asteroids," discovered ? What discovery ia 
regarded as the grand triumph of Astronomy ? What was the 
circumstances of this discovery, and who the persons engaged in 
it? — 3. What are Aerolites? Which of these phenomena are 
of common occurrence ? Which are rare ? 

23 



266 AEROLITES. 

logical knowledge of the most ancient of Aerolites on 
record, we are indebted, says Humboldt, " to the industry 
of the all-registering Chinese," by whom they were ob- 
served about 600 years before Christ. The fall of the 
heated stone at Egos Potamos, whose weight u was equal 
to a full wagon load," took place 465 years before Christ; 
and it is remarkable that the hypothesis which Anaxago- 
ras of Clazomene formed to account for its existence, is in 
its main features still adopted. Meteoric stones are still 
regarded as not parts of the Earth, but as portions of 
bodies foreign to it, and revolving either about it or about 
the Sun, and to this day no other direct proof exists, that 
bodies foreign to the earth are composed of the same ma- 
terials. " Meteoric stones/ ' says Humboldt, " appear to 
be parts of small asteroids, revolving around the Sun, and 
which coming in contact with the atmosphere of the 
Earth move in it so swiftly as to ignite by friction, explode, 
and fall in fragments to the Earth." The matter of which 
these fragments or meteoric stones are composed, is, in its 
ultimate elements, oxygen, nitrogen, and other gases, such 
as the Earth's matter is composed of, but in their com- 
pounds they are sometimes different. They have much 
iron in their composition, mingled with nickel. If there- 
fore meteoric stones are a specimen of the matter contained 
in the planets and other bodies exterior to the Earth, those 
bodies will have a general uniformity in this respect with 
the Earth, while the composition of their masses will 
show, that nature, with regard to them, will have mani- 
fested her usual variety. 

4. Until within a few years, many doubted the existence 
of such foreign masses of matter, notwithstanding well-au- 
thenticated accounts of the fall of Meteoric Stones. But 



3. What, in regard to the history of aerolites, is said of the 
Chinese ? When occurred the fall of the Meteoric Stone at Egos 
Potamos ? What is remarkable in the teachings of Anaxagoras 
concerning this Meteoric Stone ? What is Humboldt's definition 
of Meteoric Stones? What is said of the ultimate elements of the 
anatter which composes them ? Of the compounds of these ele- 
ments ? — 4. What is said concerning the belief in the existence 
of Meteoric Stones ? 



FALL OF METEORIC STONES AIGLE. 267 

On the 26th of April, 1803, such a tremendous shower 
occurred, at Aigle, in France, as furnished specimens for 
personal examination to all philosophers and every museum 
desirous of possessing them ; and from that time forward 
skepticism on this subject was at an end. The phenom- 
enon commenced by the appearance of a large fire-ball, 
which was seen to move swiftly over the neighboring 
towns. The motion of the ball was from s. e. to n. w., 
the sky being then clear. Near Aigle, it became envel- 
oped in a small black cloud, which was motionless for five 
minutes, but emitted strange and startling sounds, as of 
smaller and larger artillery. During these minutes there 
fell, on an elliptical shaped ground of 6 miles in length, a 
great number of meteoric stones, some of which weighed 
17 pounds. They were smoking and heated, but not to 
redness. These stones, on being analyzed by different 
chemists, were found to be composed of matter which, as 
remarked, was similar to that of the Earth, though differ- 
ing in some of its combinations. 

5. On this Continent, also, many other cases have occur- 
red. Meteoric Stones have, in some instances, been pro- 
jected from fire-balls with such force as to penetrate 10 
or 15 feet into the Earth. One, seen as a fire-ball, fell at 
"Weston, Connecticut, weighing 500 pounds. Although 
many Meteoric Showers have at different times taken 
place, yet the most remarkable ever known occurred in 
North America on the night of Nov. 23d, 1833. It ex- 
tended throughout the whole of the United States and into 
Mexico. Its appearance, where the fall of the Meteors 
was the greatest, was terrific. In the Southern States, to 
the slaves, awakened at the dead of night, the heavens 
seemed on fire ; and they ran screaming to their masters, 
that the day of judgment had come. The Meteors seemed 
like great snow-flakes of fire. Similar phenomena were 

4. When was skepticism at an end, and on what occasion? 
Describe the shower of aerolites at Aigle ? What was their 
weight, and of what were they composed ? — 5. When and where 
have Meteoric Stones fallen on this Continent ? Where occurred 
the most remarkable Meteoric Shower ever known '{ Describe 
this Meteoric Shower ? 



268 franklin's discovery. 

recollected to have been observed at the same season of 
the year, and the astronomer Olmsted, of New Haven, 
predicted that similar phenomena would occur at the 
same time in the years immediately succeeding. This hap- 
pening to a considerable extent, was regarded as con- 
firmatory of an ingenious theory, by which he explained 
why the Earth, in this part of her Orbit, should have 
fallen in with these Meteors. They all appeared to pro- 
ceed from the same part of the heavens, and are believed 
to have been contained within a ring or zone, within 
which they all pursue a common Orbit. 

6. Even these terrific appearances fade before a scene 
which, according to Humboldt, is related by a Latin au- 
thor as having occurred at Crema, in Italy, on the 4th 
of September, 1510. At noon-day, it suddenly became 
dark ; — a cloud of appalling blackness overshadowed the 
heavens. Upon this cloud appeared the semblance of a 
great peacock of fire flying over the town of Crema. Sud- 
denly it changed its form to a fiery pyramid traversing 
the heavens. From the intense blackness which suc- 
ceeded arose awful lightnings, and thunderings indescriba- 
ble, while there fell upon the plain, rocks, some of which 
weighed a hundred pounds.* . . . The density of Aerolites 
is to water generally as 3 to 1. 

7. Lightning is, in one sense, a part of our subject, since 
it comes from the Heavens to the Earth. The American 
philosopher Franklin, June 15, 1752, proved to the world 
the identity of the Electric Fluid with Lightning, and 
thereby taught how, by providing suitable conductors, life 
and property may be guarded. Another American phi- 

* This description occurs in a note in the first volume of 
the a Cosmos." Humboldt says it may be exaggerated, but of 
the main facts there is no doubt. 



5. From what circumstances, observed by Professor Olmsted, 
did he predict the recurrence of a Meteoric Shower at the same 
season of the year ? What is supposed concerning these numer- 
ous and small meteors ? — 6. What terrible appearance is related to 
have occurred at Crema in Italy ? What is the common density 
of aerolites ? — 7. What great discovery concerning lightning was 
made ? By whom ? When ? 



A BRIGHT STAR APPEARS. 269 

losopher, Morse, invented, 1832, the Electro-Magnetic 
Telegraph, by which Electricity and Magnetism, those 
subtle and viewless agents of the atmosphere, transmit 
with their own velocity, man's thoughts over the face of 
his planetary home. 

8. No one race of men, of whatever ability, could have 

£pleted the Science of Astronomy. It needs the ob- 
ations made and recorded of succeeding races. By 
.„e it is known that important changes take place 
among the Fixed Stars. Those which one race alone 
would have regarded as perfectly motionless, are thus 
known to have moved. Ptolemy, in the Almagest, enu- 
merates six stars as fiery red, one of which was Sirius, 
which now shines with a white light. Stars have, there- 
fore, changed their color. There were certain stars whose 
places were well defined, which are not now seen. Others 
appear and disappear at certain well-defined periods ; and 
many are now catalogued not formerly known. 

9. Of the sudden appearance and disappearance of a 
heavenly body, bearing all the characters of a fixed star, 
the most remarkable is that which appeared in the con- 
stellation Cassiopeia, on the 8th of November, 1572. 
Tycho Brahe, who was at the time on one of the Danish 
islands, says, that as he was walking in the evening, it 
suddenly broke forth with a brightness which exceeded 
Sirius, Lyra, or Jupiter, and was equal to Venus when 
nearest the Earth. Wagoners and common people, in dif- 
ferent parts of Europe, hastened to the Astronomers to ask 
the cause of this unwonted phenomenon. At night, when 
the sky was partially overcast, so that other stars were 
hidden, this alone was visible, and even .at noon-day it 

7. What other American is famous for a great invention ? 
"What is the nature and what the effect of this invention ? — 8. 
How does it appear that no one race of men could have perfected 
the Science of Astronomy ? What is now known by comparing 
the Stars with former recorded observations concerning them ? 
What change in the color of a star is mentioned, and how is it 
known ? What other changes among the Stars have occurred ? 
— 9. What is the most remarkable appearance and disappearance 
of a star on record ? By whom was it observed, and when ? How 
is its appearance described by that Astronomer? 

23* 



270 THE STAR DISAPPEARS. 

could be seen by some. It had none of the character of a 
Comet, but its light was precisely like that of a fixed star, 
except that it scintillated more. Thus it blazed for two 
months ; then, in December, its brilliancy began to dimin- 
ish. Its color, which had at first been white, had changed 
through yellow to the fiery redness of Mars. Then it faded 
to the size and color of Aldebaran. Continuing to dimin- 
ish in size, its white color returned, and finally, in March, 
15*74, it wholly faded away, and has never reappeared. 
Some believe this to have been the final conflagration of 
a world, and suppose it may have been the blaze of the 
elements at the creation of some new and now dark body. 
It is believed that such exist, and some of immense size, 
amidst the luminous fixed stars. 

10. That portion of the labors of Sir William Herschel 
and his son, which have most extended the science of As- 
tronomy, has been made in the region of the Fixed Stars. 
The contrast of what the Heavens were in respect to these 
after their discoveries, as compared with the meagerness 
of former times, will appear by considering that the cata- 
logue of Hipparchus, about 130 b. c, contained only 1080 ; 
that of Ptolemy, 250 a. c, 1225 ; and Tycho Brahe's cata- 
logue did not exceed this number. These catalogues in- 
cluded not the smallest of the visible stars, but all suffi- 
ciently distinct to be clearly and minutely described. But 
as soon as Galileo turned the newly-invented telescope to 
the Heavens,* stars, before barely visible to the naked eye, 
shone distinctly, while the invisible now first appeared. 

* "It was not," says Humboldt, "till the invention of the 
telescope, that mankind attained to the possession of the Celes- 
tial Sphere of the Cosmos." 

9. Could it have been a Comet? How long before it began 
to fade ? and how long before it finally disappeared ? What sup- 
positions are made to account for this remarkable phenomenon ? 
— 10. What is said of the labors of the two Herschels ? What 
contrast is shown by examining ancient catalogues of Fixed Stars ? 
How many did that of Hipparchus contain ? that of Ptolemy ? of 
Tycho Brahe ? What stars were not included in these cata- 
logues, and what were ? What change was made by the first 
telescope ? What in regard to the milky-clouded spots or neb- 
ulous parts of the Heavens t 



THE SOUTHERN HEAVENS. 271 

He noticed that the milky whiteness of some parts of the 
sky, by examination with the telescope, became clusters ot 
stars. Huygens discovered the Nebulae in Orion's Sword. 
Previous to this period, nothing had been said of those 
clouded portions of the sky which have since, as nebular 
phenomena, received so much attention. The southern 
part of the heavens was unknown until described by the 
navigators who followed in the track of Columbus, and 
Pinzon was the first to bring their peculiarities into no- 
tice. The two Magellanic Clouds, the greater and the 
lesser collection of Nebulae, then became known ; and also 
those dark spots called the Coal Sacks, one of which is in 
the Southern Cross, to which the telescope being pointed, 
the astronomer seems to have looked through creation into 
the infinitude of space. 

11. But previous to the labors of Sir William Herschel, 
which commenced in 1779, the Fixed Stars were studied 
without method ; and although, after the invention of the 
telescope, they were supposed to be very numerous, yet in 
this respect it was left to him to bring wonders to light. 
Halley and Lacaille had speculated upon Nebulae, and of 
these cloudy spots, not more than 2000 had been enumer- 
ated. Of Binary stars, from which so much has since 
been learned and conjectured, Sir William Herschel was 
acquainted with only four at the period when, having 
provided himself a telescope far exceeding in power any 
former one, his mind conceived the great idea of examining 
the Heavens, after a method by which, from successive 
fields of the azure dome of the Heavens, he could obtain 
certain information of the stars telescopically visible, and 
data for calculation, concerning similar parts of the Heav- 
ens not actually examined ; and that thus a grand calcula- 



10. How did the discovery of Columbus enlarge the field of 
the Astronomer? By whom were the Southern Heavens first 
described ? What peculiar appearances of the Southern Skies 
then became known ? — 11. How was the study of the Fixed Stars 
pursued previous to the time of Sir William Herschel ? What is 
said concerning the supposed number of the Stars ? of the Nebu- 
lae? of Binary stars? What great idea was at this time con- 
ceived by Sir William Herschel ? and what method pursued ? 



272 STARS OF THE MILKY WAY. 

tion of the Stars and nebulous appearances of the whole 
Heavens might be made. 

12. This immense labor, called " Gauging the Heav- 
ens," Sir William Herschel began, and with the aid of his 
son and a sister, Miss Herschel, great advances were made 
during his life- time ; and since his decease, the same pro- 
cess has been continued by his son, Sir John Herschel, who 
transmitted the great telescope to the Cape of Good Hope, 
where he resided for the examination of the Southern 
Heavens ; and to him we are indebted, not only for 
continuing, with equal ability, his father's labors, but for 
giving to the world a complete* exposition of the whole 
science of Astronomy, with the sublime reasonings and 
conjectures arising from the new facts brought to light. 
The study of these facts and conjectures, will form an im- 
portant part of a more advanced course in Astronomy, as one 
statement alone of Sir John Herschel will suffice to show : 
" So crowded/' says he, " are the stars in some parts of the 
Milky Way, that, by counting the stars in a single field of 
his telescope, he (Sir W. Herschel) was led to conclude 
that 50,000 had passed under his review in a zone two de- 
grees in breadth, during a single hour's observation." 

13. Sir William Herschel gave to the world the proba- 
ble conjecture, that as the Earth, with her Moon, revolves 
about the Sun, so the Sun, with his attendant Planets and 
their Satellites, is moving around some vast invisible 
central body,* with a rate of motion at least as great. 

* Mr. Madler, a German astronomer, believes that he has dis- 
covered this central body to be Alcyone, the largest of the 
Pleiades. Sir John Herschel does not favor the idea. Alcyone 
is not, he says, central to the Milky Way. 

12. What was this method called? By whom was it pursued 
after the death of Sir William ? What was especially done by 
Sir John Herschel? Concerning the immense number of the 
stars contained in the Milky Way, what fact is quoted from Sir 
John Herschel? — 13. For what sublime and probable conjecture 
is the world indebted to Sir William Herschel ? What does Mr. 
Madler suppose he has discovered ? and what is Sir John Her- 
schePs opinion concerning it ? (See note.) On what is the argu- 
ment for the Sun's motion based ? 



the sun's motion. 273 

The argument for this motion of the Sun is based on the 
fact that, comparing past descriptions with present ap- 
pearances, the stars, in a certain part of the Heavens, viz., 
the Constellation Hercules, are apparently receding from 
each other, and their distances increasing ; a fact not to 
be accounted for on any other supposition than that our 
system is advancing in that direction, and that the Earth 
is nearer those stars now than formerly. 

14. With this sublime idea, another is associated. If 
our family of Planets, in moving around our Sun, keep 
near the plane of a certain circle, so we may suppose it 
probable, that if some immense central body, and it may 
be a dark one, has a host of suns, with attendant worlds 
encircling it, that they may be moving in orbits varying 
but little from a plane, and the whole making an im- 
mense belt or larger Zodiac. So the Herschels supposed ; 
and they believed that the Milky Way, studded with ra- 
diant stars — the interstices filled with Nebulae, that, as 
telescopes became enlarged, are more and more resolvable 
into groups of stars — is the Great Zodiacal Circle, in which 
thousands of suns, with their attendant planets, are per- 
forming their grand era, or year of years. This conjecture 
is founded upon the fact, elicited by the labors of those two 
great astronomers, that there are in the Milky Way 30 
times as many stars as there are in equal parts of the 
Heavens at a distance from it, and nearer its poles.* 

15. Lord Kosse, of Ireland, has now the largest tele- 
scope extant, by which he is able to resolve into single stars 
Nebulae which were not thus resolvable by that of the 

* So, if the Fixed Stars were invisible, would all the Planets, 
with their Satellites, appear in the Zodiac except the Aster- 
oids, which would be seen without it, as also the Comets — of 
which Kepler said there were " as many as of fishes in the sea." 
They would show themselves in every possible direction. 

14. "What other sublime idea is associated with this hypothesis ? 
What is the teaching on this subject of the Herschels? On what 
fact, and by whom elicited, is this opinion founded concerning 
the Milky Way, as the paramount circle of the whole Heavens? 
— 15. Has a telescope, larger than that of the Herschels, been 
made? 



274 THE GREATEST TELESCOPE. 

Herschels, but their discoveries and opinions have not by 
this superior telescopic power, been controverted, but rather 
established. The opinion more and more prevails, that all 
those whitish cloudy appearances of the sky, whether of the 
Milky Way, the Magellanic Clouds, or the Smaller Nebu- 
lae, are in reality congeries of stars, distant beyond the 
power of thought. 

EXERCISES. 

The scope of our work embraces both Astronomy and Geog- 
raphy, rather descriptively than philosophically treated .* 

Our last Exercise referred wholly to Astronomy, and was con- 
nected with that great scheme of the Heavens, in which the im- 
agination of two great men had been mingled, with the facts 
which they had observed and learned, — thus giving to the world 
a grand single point of view, in which to connect together in one 
system all astronomical knowledge, and bringing to the mind 
sublimer views of the Power, the Immensity, and the Majesty 
of God. 

Following this example, we are about to propose for Geography 

* When this work was put to press, the author was not fully satisfied with 
the title written ; viz., " Astronomical Geography ; or, Astronomy as connected 
with Geography ;" though, on the whole, the best which she could form from 
actually existing English words. The second line was added, because the first, 
taking Geography as the subject, and Astronomy as a mere qualifier, did not 
give sufficient prominence, according to the plan, to Astronomy. Had the 
second line alone been taken, that would have given too much. Having 
conversed on the subject with a literary friend, John 8. Tyson, Esq., of Mary- 
land, he proposed for a title the word " Astronography," sending a learned dis- 
sertation on the Greek derivation of this as of similar words; snowing that it 
differed from Astronomy, as meaning, not the laws, but a description of the 
stars. Although this was not precisely the scope of my work, yet the word had 
an English sound, and one word for a title is far better than two. As to the 
manufacturing of a word, which may be considered in one sense as a proper 
name which a parent is to give to a child, I felt no qualms of conscience. But 
if manufactured, I saw no reason why we should go back to ancient languages 
for the material. The given word, by resemblance of sound, is associated to 
the minds of all, with the two English words Astronomy and Geography. A 
girl of thirteen being asked what she should suppose the meaning of the word 
to be, replied at once, " A mixture of Astronomy and Geography. 1 ' We adopt 
the word Astronography, then, not as derived from the two Greek words 
as-pov and yj3u0<o, but the two English words; and in the title we add " Astro- 
nomical Geography," because the learned might otherwise suppose the book 
was to be merely a description of the stars; and besides, the greater part of 
the work (which was already stereotyped) was written before the word Astron- 
ography was in existence — and in reference to the term Astronomical Geog- 
raphy. 

15. What effect has a superior telescopic power produced 
respecting their discoveries I What opinion seems more and more 
to prevail ? 



man's past and future. 275 

something of a similar nature. Geography regards God in re- 
spect to his dealings with man. To account for nations as they 
are, Geography borrows from History, as History from it ; and 
when the present is combined with the past, imagination, aided 
by reason, goes forth in Geography as in Astronomy, — into the 
events of unaccomplished time, as into the regions of unknown 
space. 

Both sacred and profane history testify to the fact that man- 
kind originated in Asia, in the regions near the eastern extremity 
of the Mediterranean ; and Revelation and profane history also 
teach that there Christianity originated, — that religion which the 
infidel acknowledges to be suited to the necessities of man — the 
best he ever had, — and likely, from the present aspect of things, 
to become, at no very distant day, the religion of the whole Earth. 
Civilized men have recently been unusually moved on the sub- 
ject of the unreasonableness and barbarism of war ; and peace 
societies and congresses of delegates, from all civilized nations, 
have already begun to assemble to devise measures to insure the 
permanent harmony of the world. 

Let the student here take the Terrestrial Globe, and examine 
it in reference to this point. Suppose the principal governments 
now existing, should take up the reasonable and righteous deter- 
mination, that an authoritative Council of Peace, to settle the 
differences and quarrels of nations, should be permanently estab- 
lished; to which every people might appeal, and where the weaker 
might have justice against the stronger — where, in such a case, 
should this council assemble ? 

•' Of this vast rale, say where shall be the seat ? 
"Where, on Earth's face, Earth's delegates shall meet ?" 

What place would be the most convenient for members and 
petitioners to assemble from all lands ? We believe it will be 
found, on the strictest examination, to be the same region of the 
world where God first showed the glories of his power and the 
wonders of his love, in creation and redemption. 

Do not take this assertion on trust, but faithfully examine the 
globe in reference to it, — keeping in view the improvements made 
and in progress, in locomotion by steam, both by land and sea. 
And as you examine, mark how easy it would be for a Congress of 
all Nations to assemble near the eastern shore of the Mediter- 
ranean ; reckoning from the capitals of the several nations now 
existing. Put Jerusalem into the upper vertex of the globe. 
Imagine the Holy City to be the place where the grand Council of 
Peace shall assemble — there being a railroad to connect it with the 
coast of the Mediterranean — and suppose yourself an Observer. 
Now apply to the Globe the same system of Almacantars as 
formerly at New York, and then take a rapid view of the land 
and water contained severally in the six belts. The first and 
second will be nearly all land, while their opposites, the fourth 



276 ONE POINT OF VIEW. 

and sixth, will be nearly all water. The two on each side of the 
Horizon will contain most of the Western Continent. But the in- 
habitants are mostly on the eastern side. The capitals of the great- 
est nations of the Western Continent, Washington and Rio Janeiro, 
are, the first above and the last scarce below the Horizon, and of 
course each but about 6000 miles distant from Jerusalem. In South 
America mark how narrow is the strip of land along the Pacific 
coast, west of the Andes ; and how the great streams, rising in their 
summits and gathering by a thousand navigable affluents into three 
great rivers, discharge themselves on the eastern coast into 
the Atlantic Ocean, on an arm of which is the Holy Land. As 
to North America, on the eastern shore stands the capital of its 
Great Republic, and the remotest west will soon be connected to 
it by a railroad. The inhabitants of the British dominions also 
gather to their provincial capitals on the east. The region in 
which Jerusalem is situated is, therefore, the place where the in- 
habitants of the world could the most conveniently assemble. 

To give interest to this peculiar examination of the geographi- 
cal position of every nation of the globe, let us now examine a 
few of the proofs that such a Council is actually to be held here- 
after, and to be held not merely in that region, but actually at Je- 
rusalem itself. — Mankind, as they become more enlightened, must 
more and more see a truth apparent to an intelligent child, that 
war is a great detriment to the human race ; wicked, when, being 
appealed to from ambition, strong nations thus affright and injure 
the weak, until the grieved and unwilling people are obliged to re- 
linquish their territories or their nationality ; or, if appealed to by 
the oppressed, it is but a hopeless and delusive remedy ; it is but 
to wade — like the Poles and the Hungarians — through blood to 
greater degradation ; or, if war be resorted to, as in the present 
case of England and France against Russia, the strong against the 
strong, the mutual injury is certain, — the result is subject to the 
casualties of storms at sea, of blight and pestilence on land, as 
well as to the chances of battle. 

Even statesmen who make war, and brave men who fight battles, 
alike bear testimony that war is a detriment to mankind, and 
only justifiable in self-defence, or because there is no other more 
rational resort against ambitious aggression. 

Such a tribunal as we have supposed, is a means, and the only 
human means, to prevent war. The greatest king of France, 
Henry IV., had the wisdom and the benevolence to plan for Eu- 
rope, such a confederation as is here supposed, to exist among all 
nations ; and the greatest and wisest of ministers, Sully, believed 
his plan to be feasible, and began actual operations. The thirty 
nations of the Republic of America, are by such a confederation 
kept in peace, amidst the most exciting differences of political 
institutions, and of religious opinions. The nations will then, soon- 
er or later, seek Peace by a similar confederacy, which shall leave 
to each its own peculiar government. But a meeting of nations 



A TERRESTRIAL GALAXY. 277 

would naturally promote the interests of all, by making the 
wants of each known to those who wish to supply them, and by 
diffusing the knowledge of all improvements. 

And we believe, as confidently as the astronomer believes that 
the Milky Way is the Zodiac of Zodiacs, that the world is des- 
tined to be ruled, in matters of national law, by a government of 
governments; and we believe that this tribunal will have its ter- 
restrial seat at Jerusalem. For the nations who even now bear 
sway in the world are Christian nations ; and whatever may be 
the religious belief of their rulers, they know that to the hearU 
of their people, there is on the face of the earth, no place like 
Jerusalem, — no hills like those of Sion and Calvary, and no 
gardens like those of Gethsemane and Joseph of Arimathea, 
Few believe that either Nicholas of Russia or Napoleon III. have 
been actuated by personal feeling in the late contest concerning 
the Holy Places — but that they seek for popularity, being aware 
of the power of these sacred associations over the hearts of the 
people. None of the more powerful nations would be permitted 
by the others to become the metropolis of the world ; nor would 
any existing government be willing to give itself, within its 
own territory, what would, in some respects, be its superior. 
The Holy Land might be obtained for this purpose, as the District 
of Columbia for the general government of the United States of 
America, The Jews now have the wealth and the desire to 
purchase Palestine, and surely they would rejoice that their be- 
loved city should, as foretold by their prophets, have " the glory of 
all lands flow into her/' 

With the ships which brought the Gentile delegates to the port 
of Jerusalem, its ancient people, who for nearly 2000 years have 
shown the single example of a nation without a place, would 
naturally return there, believing that the Author of Christianity 
had been proved the Restorer of their Nation. The riches of 
the world would concentrate ; and soon would arise in splendor, 
a " New Jerusalem." 

Nor war nor waste her borders more shall see, 
And the whole Earth her happy borders be.* 



* The concluding lines of a poem on the same subject written and publish- 
ed by the author in 1S20. 

24 



CHAPTER XXVI. 

Atheism Unphilosophical. — God is especially Manifested in 
Adaptations. — Man is adapted to the Earth, the Air, and 
the Sun, and they to him. — Man's dignified Position — His 
Immortality — His high Moral and Religious Duties Illus- 
trated by Gravitation. 

1. Heaven and Earth are full of the Majesty of God's 
glory. Of this, if any of our young learners are not now 
more fully convinced than before they studied this book, 
then, to them, has it been comparatively useless ; for they 
will have missed the most valuable of its intended benefits. 
But if this work shall have led them to join the glorious 
company of those who delight in praise to God, then will 
it have achieved a nobler task than that of the proudest 
astronomical philosopher, who, with vast learning, writes 
Systems of the worlds, taking no note of their Maker — 
the self-existent God — the all-pervading Spirit of the Uni- 
verse. 

2. We know that efforts, like those we are now about to 
make, to show " the Eternal Power and Godhead, by the 
things which are made," are apt to be looked upon by such 
writers with cold contempt, as wholly unphilosophical. 
We not only repel such a charge, but we return it. Would 
he who should write a treatise on Man, and make no men- 
tion of his Mind, be truly logical and philosophical ? As 
little so, is he who writes a system of the visible Universe, 
and makes no mention of its God. 



Chapter XXVI. — 1. "With what assertion does the Chapter 
commence ? In what case would your author regard her work 
as comparatively useless? In a contrary case, how would she 
compare the effect of her labors with some of those who are her 
superiors in learning? — 2. What does your author say of cer- 
tain views of such writers ? How would she receive such a 
charge concerning her own work ? What two things does she 
compare, regarding them as equally illogical and unphilosophical ? 



THEORY OF LA PLACE. 279 

3. The great mathematical astronomer, La Place, as if 
to show that Creation itself might have been but the un- 
designing action of inanimate matter, has produced a 
grand theory by which he undertakes to show, that if 
we grant the existence of a mighty mass of matter, equal 
in quantity to that contained in the whole Solar System, 
already having received the form of a ring or rings, sim- 
ilar in shape to those of Saturn, endued with gravitation, 
and already whirling with a given centrifugal force, then, 
that such a ring or rings might, by their gyrations, throw 
off such bodies as the Planets of our System, and still have 
sufficient remaining for a great body to occupy the centre. 
Suppose this theory — which can never be proved, and 
which would be perfectly useless if it were— suppose it to 
be true ; and what then ? Atheism gains nothing by it. 
If such was the best way to make the worlds, it was no 
doubt the method by which God made them. But for 
the possession and balancing of forces, by which action 
should be given to such immense masses, and for such 
sublimely intelligent ends, from whence did these unintelli- 
gent collections of atoms receive it ? In the language of 
the poet Young, we ask : 

" Who, Motion, foreign to the smallest grain, 
Shot through vast masses of enormous weight ?" 

And how — if the w T orlds were chance-directed — how comes 
it that they have taken their places in such magnificent 
order — that though the Heavens are studded with worlds 
sweeping circuits beyond the reach of thought, yet System 
never interferes with System, nor world with world ? 

4. But should any be so irrational as to maintain that 
dead matter, in its great masses, is self-endued with the 
centripetal and centrifugal forces, and that by these the 

3. For what purpose does La Place seem to have introduced 
his theory of worlds ? What are we to take for granted in this 
theory ? And what is the supposed consequence, or what might 
then happen, according to this theory? Suppose this theory 
true, what then ? Is it credible that such a collection of unin- 
telligent atoms should, of themselves and by chance, produce 
worlds and set them in such harmonious motion ? 



280 ADAPTATION PROVES DESIGN. 

Planets have been thrown off from a great gyrating ring, 
and set to rolling and revolving in harmonious order — 
whence, we ask again — whence are the living forms, 
vegetable and animal, which adorn and people the earth ? 
"What is there in all dead matter, even if endued with 
these blind forces, that could have produced the lowliest 
plant which creeps beneath the oak of the forest ? And 
who, then, made the oak ? Who made the strong lion 
under its foliage, and the melodious bird, whose nest is 
in its branches ? And more than all, who made Man, 
with his majestic form and godlike faculties, — beneath 
whose intelligent eye the monarch of the forest quails, and 
acknowledges him the regent of this lower world — the 
chief inhabitant, and the intelligent Ruler of the Earth ? 

5. There is in our day a fashionable kind of Atheism 
which professes to find a Divinity in Nature. But what 
is Nature ? A mere word expressing effects. It does not 
imply an intelligent, designing Cause. But one great 
designing first Cause of all things there must be ; plan- 
ning, with Infinite Benevolence, to bring forth the great- 
est good ; devising, with Infinite Wisdom, the best means, 
and executing them with Infinite Power. 

6. The adaptation of all things one to another, no less 
than Creation itself, proves the Existence, the Unity, and 
the Attributes of God. Let us take a single example, 
Man ; and let us observe how he is suited to other things, 
and they to him. When he is first ushered into the world, 
there is the dormant spark of life residing in his lungs ; 
but it must, at the instant, and during every instant of 
his life, be rekindled and revivified by an external sub- 

4. But suppose that any should be so irrational as to maintain 
that great masses of matter might be self-endued with innate 
forces, what questions might then be asked ? — 5. What is here said 
of Nature ? What does the term Nature not imply ? Since we 
produce evidences of design, what must there be ? Which of 
the terms used expresses the Unity of God ? What three terms in 
the sentence express the infinite attributes of God ? — 6. What, 
equally with Creation, proves the existence, unity, and attributes 
of God ? What example is chosen, and what are we to observe ? 
What has man when first ushered into the world ? How must 
this be revivified? 



• INSTINCT OF RESPIRATION. 281 

stance constantly brought in contact with it. Is this ex- 
ternal substance made, and at hand, and has the infant 
been provided with a proper physical organization to draw 
it inwards to the lungs ? AH has been well done. The 
substance, without which he immediately dies, is the at- 
mosphere which surrounds the globe, and which, from its 
pressure in all directions, must ever envelop him. 

7. By his physical organization Man is not only ena- 
bled, but compelled to receive air into his lungs, and to 
retain it until it has imparted the needful oxygen, and 
then to expel the hurtful residuum. Man's bony frame, 
his muscles, and his nerves, are all arranged with the spe- 
cial object of producing this effect. His ribs are so artic- 
ulated to his spine as to rise — the muscles being made to 
conspire — giving breadth to the chest, and thus producing 
a vacuum, which irresistibly draws in the air ; and then 
the same ribs fall, narrowing the chest, and forcing out 
the unwholesome carbonic gas, which remains after the 
oxygen of the inspired air has been imparted to the car- 
bon of the blood. And thus is the fire of life, every mo- 
ment while life lasts, rekindled and revivified at the lungs ; 
and thus is shown the adaptation of Man to the Air, and 
of the Air to Man. 

8. There is another portion of this vital process of 
breathing — Man's first and last act — by which is equally 
shown that he is designedly adapted to the Earth and the 
Earth to him. In the animal combustion — which, as we 
have seen, must be constantly kept up by respiration — there 
must be carbon to be burned, as well as oxygen in which to 
bu?-n it. And whence comes this carbon-fuel ? From the 
Earth. To furnish it was the special object for which the 
vegetable world was created. Plants are either man's im- 



6. What questions are here asked? How are they answered? 
— 7. What parts of man's body are arranged with special refer- 
ence to his breathing ? In what way are his ribs articulated or 
joined to his backbone ? and what is every moment accomplished 
by this ? What is thus shown ? — 8. What is here incidentally as- 
serted of breathing? What does your author now propose to 
show ? What is said concerning the animal combustion which 
the oxygen of the air supports ? Whence comes this carbon-fuel ? 
24* 



282 FKOM GOD ARE MAK 5 S WANTS, 

mediate aliment, or they are that of the. animals on which 
he feeds. And Water to dilute this food, and furnish 
the substratum of the blood into which it must be formed, 
before it can be taken to the lungs by the pipes prepared 
to convey it— water is no less a necessary to man than 
food ; and liberally is the Earth prepared to furnish it. 
Next to the air, it is the freest and most abundant thing 
on the surface of the globe. And is man's physical sys- 
tem so made that he can receive, and reduce to its proper 
state for breathing, this necessary but unprepared carbon ? 
Expressly is the physical man formed for eating, drinking, 
and digestion. Then as you observe his mouth, his teeth, 
his stomach, and other organs of digestion, and at the 
same time look abroad upon the waving bread-fields of 
the Earth, devoutly say that man was formed for them, as 
they for him, by the same infinite Intelligence. 

9. Man's designed adaptedness to the things around 
him, is as clearly shown by his instincts as by his phys- 
ical frame. Had it been left to his discretion and judg- 
ment whether he would choose to breathe or not, in vain 
might God have made the lungs and the air. But to 
make sure of his purpose, he has added the irresistible 
instinct of respiration, which compels Man to breathe, so 
that he cannot, if he would, shut that door of his life. 
He is obliged to take water by the instinct of thirst, and 
food by that of hunger. And the benevolence of the 
Deity has added the instincts of pleasure, by which man 
is invited to take his necessary aliment, to those of pain, 
by which he is compelled. 

10. And equally are the wisdom and goodness of God 
indicated by the instinct of warmth. By this we mean 
the sense of comfort in warmth, and of pain in cold- 
ness. Man does not live to breathe : he breathes to live. 
The great function of life to which breathing is subservi- 

8. What is said of water ? For what is the physical man ex- 
pressly formed ? What should we then observe together, and 
what conclusion form? — 9. By what besides his physical frame is 
man's adaptedness to the things around him shown ? What in- 
stincts are first mentioned ? — 10. What is meant by the instinct 
of warmth ? 



FHOM GOD THE SUPPLY. 283 

ent, is the Circulation of the Blood. By this, sustenance 
is carried to every part of the body, to supply the waste, 
or increase the growth. If circulation fails, death ensues. 
But it must fail, unless there is kept up a due balance be- 
tween that interior heat, which is caused by animal com- 
bustion at the lungs, and that exterior coldness, which is 
caused by the conducting of the heat from the surface of 
the body by the atmosphere. A due balance is indicated 
by a medium temperature of 98° Fahrenheit, which must 
be preserved by all races of men in all climates of the 
Earth. This delicate balance* must be rightly adjusted, or 
circulation stops, and man dies. But how is this balance 
to be preserved ? Has Man within him a hidden ther- 
mometer by which it is adjusted ? God has given him 
one which will never deceive him. It is his instinctive 
genial pleasure in a just degree of warmth, and a sense of 
discomfort in coldness, as soon as it becomes hurtful, and 
of intolerable pain when it is destructive. 

11. It is by this instinct of warmth that Man is both 
invited and compelled to clothe himself; and the more 
heavily as his climate grows the more cold : threatening 
otherwise to carry off the heat of his body ; so as to de- 
stroy the necessary balance. For the same reason, he is 
obliged to build houses for himself and his children. But 
fear not : he who is the Author of Man's necessities is the 
same who provides for their supply. See, for his clothing, 
the flax, the cotton, the wool, and the fur ; and to con- 
struct his dwelling, behold the trees of the forest, the iron 
of the mine, and the stones of the quarry. 

12. But clothe and shelter himself as he may, Man, in 
very high latitudes, breathes a condensed air, containing 

10. What does your author consider to be the great function 
of life to which breathing is subservient ? What is the use of the 
circulation of the blood ? But in what case must the circulation 
fail ? What is said of the medium temperature of the human 
body ? What questions are here put concerning the due bal- 
ance of heat and coldness ? How are they answered ? — 11. What 
is further said of the instinct of warmth ? Will man find provi- 
sion for these great necessities? — 12. But how will it be with the 
inhabitants of high latitudes in regard to the proper balance of 
heat and cold ? 



284 SPECIAL ADAPTATIONS. 

much oxygen ; and sharp cold comes to him externally* 
But here his instincts lead him to seek such aliment, as 
the inhabitant of the Equator would loathe ; and hence 
he feeds on oily matters, yielding to the blood much car- 
bon — to meet at the lungs the extra quantity of oxygen ; 
thus keeping up a glowing fire at the centre, — balancing 
the intense cold without, and keeping up the normal tem- 
perature. 

13. Thus we see, that not only has the Deity wrought a 
general adaptation of Man and the things around him, 
but, as if to manifest that he works by no necessity, 
but by an intelligent choice, he makes special adapta- 
tions, by which he varies his general plans to suit par- 
ticular circumstances. Thus, while the dweller in the 
Frigid Zone has an appetite for tallow, the inhabi- 
tants of the Torrid desires nothing but the cooling 
fruits which his climate alone produces. These afford all 
the carbon needed to meet the small quantity of oxygen 
afforded to the lungs by his sun-expanded atmosphere. 
If the fire of life burns feebly within, there is no intense 
cold without ; nay, there is too little external cold for the 
circulation ; and, by more copious perspiration, which takes 
heat from the surface of the body to convert it into vapor, 
the Almighty makes another special provision to keep up, 
in warm climates, the due healthful balance. 

14. The exterior organs of respiration are also varied in 
the different races to receive a greater or less bulk of air, 
according to its expansion by heat or condensation by cold, 
in the different regions which they are formed to inhabit. 
The white race, made for the Temperate Zones, inspire 
through slender noses, bending downwards, but a small 
bulk of air compared with the negro, who spreads the 
broad unobstructed nostril to the heat-attenuated breeze ; 
while he is furnished with a skin, which, by its porous tex- 

13. What do Special Adaptations manifest respecting the 
Deity ? In these how does he vary his general plans ? By what 
arrangements is the healthful balance kept up in the Torrid 
regions ? — 14. What is said of the special adaptedness of the ex- 
terior organs of respiration to the climate of particular races of 
men? 



MAN MADE FOE THE EARTH. 285 

ture, freely exudes in perspiration the water of the blood, 
thus furnishing the material to keep up a constant cool- 
ness on the surface of the body by evaporation. 

15. Thus man, in every breath which he draws, shows 
that his Maker has adapted him to the Earth and the air, 
and that they are made expressly for him ; and our Science 
carries us farther. It shows us that Man was made for 
the Sun, and the Sun for him. It is by means of the Sun 
that the Earth brings forth his food, that liquid water 
flows, and that the atmosphere is sufficiently warmed and 
expanded for man's respiration. But man has an organ 
which unmistakably connects him with the Sun. It is the 
eye — the eye, which is the gem of the animal creation. 
It was made for light, and light emanating from the Sun 
was made for the eye. 

16. And with this more delicate organ our indulgent 
Father has connected higher and finer instincts, — the sense 
of beauty, and the love of knowledge. And how gloriously 
has he wrought to supply these desires, and to make them 
the means of virtue and enjoyment to his sentient and 
rational children ! How beautiful and how sublime has 
he made the forms of external things ! He has con- 
nected man with the Starry Heavens as well as with the 
Sun, by his desire to know them, and his perception of 
their beauty ; and ever, when he becomes wearied amidst 
the glare of day, the. Earth shall turn upon her axis, and 
bring him, with the starry night, repose in sleep : sleep — 
that emblem of death, from which he shall, in the morn- 
ing, have a resurrection to renewed existence. And can 
we look at these facts, and not believe in one, designing, 
wise, and benevolent God ? And shall we call it 
philosophy to stand and doubt ? And must we be called 
credulous who believe ? As well call him credulous 
who, seeing an infant wrapped and asleep in his cradle, 

15. What is here said of the Sun in reference to Man ? How 
is it proved that the Sun was made for man, and man for the 
Sun? — 16. What instincts has our indulgent Father connected 
with the Eye ? How has God wrought to supply these desires ? 
What arrangement is made that man may sleep ? What ques- 
tions are here asked ? How are they answered ? 



286 THE EAETH MADE FOR MAN. 

believes that the child has an intelligent mother, who has 
done for him what he was not able to do for himself ; — 
and as well may we call that logic and philosophy, which, 
not having seen the mother, denies that there is one, and 
laughs at the idea, that the cradle was designed expressly 
for the babe. 

17. Man is the child of God. His nutrition, and 
his vestments are derived from that Earth which God 
has made for his use. And he cannot be shaken from her 
maternal embrace, because of that part of the law of grav- 
itation by which nearness binds more closely than quan- 
tity of matter ; while, by the other portion of the same law, 
the great mass of matter which, by the Almighty, is 
placed in the central body of the Solar System, so biuds 
the Earth with the other Planets, that they cannot wander 
from their spheres. 

18. God has made the Earth for man. Is the house 
regarded by the Father who has built it, as of more value 
than the child who inhabits it, and for whom it was made ? 
And will He keep the house and not preserve the child ? 
It cannot be. And if man, in the wise use of that agency 
by which he is ennobled, shall become a co-worker with 
God for good, then shall he be preserved, though his body 
shall all perish, except that germ of immortality which the 
Lord, according to his Word, will keep from destruction, 
raise from the dead, and to which he will give such a body 
as shall please Himself. 

19. Let Man, then, appreciate his own dignified and re- 
sponsible position in the Universe. Let him study his 
Maker's will. To this end, let him yield a profound atten- 
tion to the great lesson taught him by the connection which 



17. How does it appear that man is the child of God ? What 
does Astronomy teach which shows that man cannot be shaken 
from the Earth ? what which shows that the Earth cannot wan- 
der from her sphere and deprive man of the light and warmth of 
the Sun ? — 18. This paragraph contains an argument for the im- 
mortality, especially of those who make themselves co-workers 
with God for good : — can you state the argument, with the con- 
clusion ? — 19. What should man do in reference to his position 
in the Universe ? 



CONCLUSION. 287 

the Author of Nature has established between Time, Space, 
and Motion. The Sun apparently passing over 15° in an 
hour, and in 24 completing his daily circle — what is it but 
a great diurnal clock ? And what is the Ecliptic but a 
grand annual Chronometer, where the Sun describes, with 
invariable regularity, his twelve star-marked periods, and 
which, as the last is completed, strikes the knell of another 
of those yearly courses which, to man, divides Time from 
Eternity ? And shall the Sun, the Earth, and the Planets 
each have its revolution to perform in Time and in Space, 
and shall Man complain that he "hath his daily work of 
body or mind appointed !" or shall he alone be a laggard 
in his sphere ? 

20. There is a Moral Gravitation, as well as a natural. 
It is beautifully recognized in our Saviour's summary of 
the great Law of Love. Intelligent beings are by this to 
gravitate first towards the Creator, himself infinitely 
greater in all perfections than all his creatures combined. 
But as the Earth and the Moon, influenced by the gravity 
of nearness, revolve around their common centre of union, 
yet cease not to move together around the Sun, so may 
the good, allied by consanguinity or friendship, revolve 
around each other, so they never violate that higher moral 
attraction, which binds them to God. 

19. What lesson has our Science taught him to which he should 
pay profound attention ? Recite the succeeding passage respect- 
ing Time, Space, and Motion. — 20. Recite the concluding passage 
in which your author illustrates the two branches of the great 
law of love to God and love to man by the two parts of the law 
of natural gravitation. 



INDEX. 



Aerolites — shooting-stars— fire-balls — and meteoric stones, 265-=6. 

Shower of aerolites, at Aigle, in France, 267. — Meteoric shower 

in N. America, 268.— Terrific fall of meteoric rocks at Crema, 

in Italy, 268. 
Alexander the Great, 28, 244-5. 
Altitude of any heavenly body, 54. 
Almacantar Circles — terrestrial, 64-5 — celestial, 66. — Five Al- 

macantar Circles used to divide the Earth into Six Belts or 

Zones, 92-5. — Breadth of each Almaoantar Zone, 96. — Square 

miles in each, 97. 
Almagest of Ptolemy, 250-1. 
Al-Mamun, 251. 
Alphonso X. of Castile, 249. 
Amplitude of a heavenly body, 54. 
Analemma, 90. 
Anaxagoras. 242. 
A?iaxi?nander, 242. 
Angular Distance, 22. 
Angular Motion, 22. 
Antceci, 185. 
Aphelion, 156. 
Apogee, 156. 
Arabians — cultivate Mathematics and Astronomy under the 

caliphs, 251. 
Arago, 264. 
Archimedes, 245. 
Aristotle, 24:4:. 
Asteroids, 33— table of, 39. 

25 



290 INDEX. 

Astronography— -a word composed of parts of the two English 

words Astronomy and Geography, 16. — Note on, 274. 
Astronomy — definition — derivation, 16. — Antiquity, 28. — First 

studied in China, 238-9 — in India — in Phenicia — in Egypt — 

and in Greece, 240. 
Atmosphere, or Air — man's element, in which only he exists, by 

Respiration, 140. — Its height — gravitation — the barometer — 

aerial tides, 141-2. — Its influence, by motion, <fec, on climate, 

197. 
Axis of the Earth — an axis of permanent positions — determinate, 

though not material — becomes by extension the 
Axis of the Heavens, 42. 
Axis of the Ecliptic — the Axis of the System of the Heavens — 

its angle with the Earth's axis, 46. 
Azimuth of any heavenly body, 54. 

Binary Stars, 271. 
Boiling Springs, 195, 

Calendar — reformed by Julius Caesar, 232 — by Pope Gregory, 

231-2-3. 
Centrifugal force, 172. 
Centripetal force, 172. 
China and the Chinese — the well-ascertained antiquity of their 

knowledge of Astronomy and Mathematics — their ignorance of 

Geography, 238-9-40. 
Circle of Daily Motion — found by an imagined ray of solid light — 

explained and illustrated, 126. — Lengths of day and night in 

different latitudes, 126, 134, 181-2.— -Examples, 185. 
Circles of perpetual apparition — of perpetual occultation, 132. 
Circumpolar stars, 89-90. 
Climates — primary causes of difference, 190-1. — Division by 

hours — illustrated, 192-3. — Secondary causes of difference, 

194-5-6. 
Climatology (see Climates). 
Coal-sacks, 271. 

Coincident Circles — to be distinguished from identical, 208. 
Comets, divided into Interior and Exterior, 34. 
Concentric Circles, 21. 
Concentric Spheres, 22. 



INDEX. 291 

Conclusion — Principles of Natural Theology deduced from the 
subject — especially from the Adaptation of Man, not only to 
his home, the Earth, geographically considered, but also to the 
Earth's astronomical motions, and to the influences of the heav- 
enly bodies, especially the Sun, 284-5-6-7. 

Constellations — Table of the principal Constellations and their 
most brilliant Stars, 24-^5. 

Copernicus, 252-3. 

Cuvier, 237. 

Cycle — Chinese, of 60 years, 239. — Lunar Cycle — Metonic Cycle, 
241. 

Damo, 244. 

Day— the Sidereal Day, 214-15. — The Solar Day— the Day of 
mean solar time — the common Day, 216. — Causes of their dif- 
ference, 225-6. 

Declination of a heavenly body — corresponds with terrestrial lati- 
tude, 62. 

Diurnal Arc, 132. 

Diurnal Motion of the Earth explained and illustrated, 67-8-9-70. 

Earth — Man's home — its condition depends on the Sun and other 
heavenly bodies, 16. — Rot a perfect sphere — differs little — is 
an oblate spheroid, 17-18. — Doctrine of the Sphere applied to 
the Earth, 20. — 69 miles measures a degree of a great circle, 
20. — Its convexity proved by the dip of the Sensible Horizon, 
31. — By its shadow in eclipses, 102. — Its centre the astronom- 
ical point of view, 32.— Its diameter, 34. — Distance from the 
Sun, 34-5. — Annual and diurnal revolution, 35. 

Earthquakes, 195. 

Earth's annual motion, causing the Surfs apparent yearly course 
explained and illustrated, 76-7-8-9-80. 

Earth's Orbit — not the Ecliptic, but their planes coincident, 75. 

Earth's rotation on its axis, 85. 

Ecliptic — the great circle of the System of the Heavens — its 
place in the Heavens — how determined, 46. — The table of its 
12 Signs, 73. — How separated from the constellations of the 
same name, 73-4. — Four cardinal points of, 110. 

Education— of the Eye, 134, 203.— Of the Hand, 170.— Imparts 
that power of observation, by which seeing little, we know 
much — illustrated by a night-figure, 204-5-6-7-8-9. 



292 index. 

Eclipse, 75. 

Epicycles, 249. 

Equation of Time, 224-28. 

Equator, or equal divider — the great circle of the Earth's axis, 
20, 43. 

Equinoctial, or equal night — the great circle of the System of the 
Heavens, 43. 

Equinoctial Colure — its place in the Heavens known by the stars 
Cynosura, Megrez, and Caph — divided by the Poles into the 
Vernal and Autumnal (semicircular) Colures, 40. 

Equinoctial Points — the Yernal, when and how found in the 
Heavens, 61. — They belong solely to place, are not the Equi- 
noxes, but correspond with them, 61. — When the Sun is in 
them, 103-5. 

Equinoxes — belong solely to time — correspond with the Equinoc- 
tial Points — the Vernal takes precedence of the Autumnal, 
62. — When the Sun passes them, 103-4. • 

Eratosthenes, 246. 

Erythea, 246. 

Euclid, 245. 

First Secondary of the Ecliptic, or that passing through the first 
of Aries, 118. 

Fixed Stars — divided into luminous and opaJce bodies or Planets, 
which are Secondaries to the Sun, 26. — Though regarded as 
moveless, yet slight motions are detected — some have changed 
color — some newly appeared — and some disappeared, 269-70. 
— Their study first systematized by Sir William Herschel, 
271. 

Fold — mythic founder of the Chinese empire, 240. 

Franklin, 268. 

Galactic System, 262. 

Galileo, 255-6-7. 

Galaxy — Milky Way, or Via Lactea, 27-8, 151-2. — How we may 
understand that its general form is a great circle of the Heav- 
ens — discoveries of the Herschels — their supposition respecting 
the motion in it of the Solar System, 273. 

Gaubil — a French Jesuit missionary in China, 239. 

Geocentric position of the Observer, 66. 



INDEX* 293 

Geography — derivation of the word, 16> — Dependant on Astrono- 
my for the construction of correct maps, 47. — A system of uni* 
versal Geography composed by Eratosthenes, 246. — The sci- 
ence cultivated by Strabo, 247. — By Ptolemy, 250. — Geography 
borrows from History — like Astronomy, reasons from the known 
to the unknown, 275. — Looks to the probable future — confed- 
eracy of nations to preserve peace, and consequently to one 
metropolis — probability that the Holy City may become, in 
future time, this metropolis, 275-7. 

Globe, Celestial — differs from the Terrestrial — represents the vast 
concave of the Heavens — shows the place of the Constellations, 
24. — How it represents, at any moment, the actual Heavens, 
29. 

Globe, Terrestrial— differs from the Celestial, 24. — The one in 
common use — made for a definite longitude, and a certain 
minute in the year, 83-4. 

Gravitation — attraction of — draws all terrestrial objects to the 
Earth's centre, 16. — Law of, 158. — Discovered by Newton, 160. 

Greek Alphabet, 98. 

Heliocentric position of the Observer, 66. 

Herschel, Sir John — his opinion respecting the proof of the 
Earth's convexity, 31.— -Quotation from his " Outlines of 
Astronomy," giving a comparative view of the different bodies 
of the Solar System, 37. — His discoveries, 265. 

Herschel, Sir William-— his great services to Astronomy, 265. 

Hesperus (see Yenus). 

Hoan-ti, 238. 

Horizon — the rational — the great circle of the Observer's Line — 
its concentric great celestial circle, the Horizon of the Heav- 
ens, 45. — Of the six terrestrial Almacantar Circles, the third, 
93-5. 

Hour Circles, or Horary Circles, 29, 84. 

Hours and Degrees convertible, 85-6. — How marked on the Time 
Circle, 87. 

Humboldt, 173, 196. — His scheme of Climatology, 200. 

Huygens, 259. 

Imagination— improved and enlarged by Astronography, 15, 238. 
Imaginary Ray of Solid Light, 126. 

25* 



294 INDEX. 

Index (see Hour Circle), 180. 

Internal Heat of the Earth, 194. 

Intersections — of the System of the Earth with the System, of the 

Heavens — produce Permanent Positions, with the exception of 

a slight movement of the one upon the other, by which the 

Equinoctial Points retrocede, 108-11. 
Intersections of the Syste?n of the Earth with that of the Observer 

— produce Movable Positions — figure to illustrate, with eight 

angles at the centre, 120-2. 
Isothermal Lines, or Isotherms, 200. 

Kepler — discovery of his laws, 253-4-5. 

La Place, 264, 

Latitude of the Earth's System — its great importance — lines of — 
accessories to the Earth's System, and mark permanent posi- 
tions — how divided into North and South, 47. — Angle of, 48- 
9. — Terrestrial arc of, 49. — Celestial arc of, 50. — Differences of 
the breadth of degrees in different longitudes, 118. — Common, 
with latitude, in giving accuracy to the locality of places as 
described by maps, 122. — How the Observer may determine his 
latitude, 123. 

Latitude of the Heavens, reckoned from the Ecliptic, 63. 

Leap-year, 231. 

Le Glerc — a French writer on Chinese history (see Note), 239. 

Le Verrier, 265. 

Light — its velocity, 26. — Discoveries of Arago, 264. 

Line of the Observer, 44. — It is the Axis of Permanent and Mov 
able Positions, 45. 

Lippershey, Hans — invents eye-glasses, which leads to the inven- 
tion of the telescope, 256. 

Longitude — celestial — the zero (0°) point, from which reckoned 
round the Ecliptic — divided by its cardinal points. 

Longitude — terrestrial, 48. — 15° to an hour, 86. — Method of find- 
ing, 88-9. — Conspires, with latitude, in giving accuracy to 
maps, 122. 

Lower Vertex, 44-5. 

Lucifer — name of the Morning Star, 153. 

Lunation — defined, 35. — Called a sidereal month — its time, 155. 



INDEX. 295 

fagellanic Light, 152, or Nebulous Clouds, 271-74. 
Taps — how made — their important uses, 51, 122. 
Magnetic Needle, 56. 
'farmer's Compass, 55. 
teridian, 47-8. 
Ji.nd — both the Instrument by whieh Astronomy is cultivated, 

and its Recipient — more wonderful than Matter, 236-7. 
? onlh, 230. 

Moon — revolution round the Earth — the favorite especially of 
sentimental poets, 153. — Its diameter — distance from the 
Earth, 154. — Its three motions — nodes — eclipses, 162. — Phases 
— course in the Zodiac — Harvest Moon, 157-8. 
Morse — discovers the Magnetic Telegraph, 269. 

Nadir — lower celestial extremity of the Observer's line, 45. 

Newton — discovers Gravitation, 259-60. 

Nocturnal Arc, 132. 

Nonegcsimal, or highest point of the Ecliptic — how found, 211- 

12. 
Noon, 218. 

Oblique Sphere, 135-6, 170. 

Observer — first Observer — must be kept in view, his mind as well 
as his place — to him many definitions solely refer, 11. — To put 
the Observer in his place, 23. — Movable Positions depend on 
his place — Observer at New York, 173, 183. — At Buenos 
Ayres— Stockholm, 186.— -At the North Pole, 187-8.— On the 
Equator at Quito, 189. 

Olmsted, Denison — his hypothesis respecting annual meteoric 
showers, 268. 

Parallax — explained and illustrated, 145-6-7. 

Parallel Sphere, 135-9. 

Perigee, 156. 

Pericles, 243. 

Perihelion, 156. 

Periodicity — time and space measure each other, 82. — The grand 

unit of time, that of the Earth's rotation, 85. 
Philolaus, 244. 
Piazzi, 265. 



296 INDEX. 

Planets**-* number and names of primary — of secondary, S3. — Su- 
perior and inferior^ 34. — Where to be looked for in the Heav- 
ens, 233-4. — Motions direct and retrograde explained and illus- 
trated, 235. 

Plato, 244. 

Points of the Compass — the four cardinal points — difficulties in 
determining them when the Observer is not on the Equator, 
56-7-8-9-60. 

Polar Circles-- -smaller circles of the Earth's axis, 20. — "Where 
placed on the Earth, 47. 

Polar Star — how found, 28. 

Poles of the Earth, 42-8, 

Poles of the Ecliptic — where found, 112. 

Poles of the Heavens, 42-3. 

Positions — Permanent — refer to things determinate by nature, 
41-2, 171. — Movable — refer to a located Observer, 41-2-4, 171. 

Precession of the Equinoxes, 74— plan of illustration, 222. — Retro- 
cession of the Equinoctial Points, 74. — How far they have 
retroceded, and what time will complete a circle, 221. 

Prime Verticals — East and West — which is called the Prime Ver- 
tical — the terrestrial not an east and west line, except at the 
Equator, 58. — The North and South Prime Vertical coincides 
entirely with the superior meridian of the Observer at the 
Equator— elsewhere, from the upper Pole to the Horizon is 
an arc, both celestial and terrestrial, whose direction is con- 
trary to the North and South Vertical, 210-11. 

Ptolemy, 249-50. 

Pythagoras, 243. 

Quadrant of Altitude, 29. 

Rainy Season, 201. 

Refection — explained and illustrated, 149-50. 

Refraction — explained and illustrated, 147-8-9-50. 

Respiration, 140, 182. 

Retrocession of the Equinoctial Points, 74. 

Rhumb-line, 59. 

Right Ascension of a heavenly body — corresponds with terrestrial 

longitude — reckoned quite round the Circle, 63. 
Right Sphere, 135-6-7. 
Rosse, Lord, of Scotland, 273. 



iotex. 297 

Schools of Antiquity, which advanced the study of Astronomy — 
the Ionian, of whom the principal astronomers were Thales, 
Anaximander, and Anaxagoras, 141-2 — the Ceotonian, of 
whom the founder was Pythagoras — and the Alexandrian, 
245 — of whom the greatest astronomer b. c. was Hipparchus, 
246 — and a, c. was Ptolemy, 249. 

Seasons of the Earth — causes of their change explained and illus- 
trated, 99-100-4. — Seasons of the planets explained, 113-14. 

Secondary to a great Circle, 47. 

Selenography, 156. 

Sensible Horizon — defined — its dip — proves the Earth's convex- 
ity, 31. 

Snow-line, 196. 

Solar System, 33. — Bodies belonging to it, 35. 

Solstitial Colare — the only secondary of the Equator which co- 
incides with a secondary of the Ecliptic, 109. 

Solstitial Points — when the Sun is in them, 103-5. 

Sphere — what was anciently called " Doctrine of the Sphere ;" 
called in modern times Spherics — Sphere synonymous with 
Globe, 17. — Definitions — Hemisphere, 19. — Radius of a Sphere 
— diameter of — great circle of — lesser circle of — circumference 
of — plane of — axis and poles of — angles of — formed at the 
centre on the plane of a great circle divided into 360°, 17- 
18-19. — Universal measure of angles of, 21. 

Spherical Systems — assumed definition — adjuncts or accessories, 
22. — Intersections, 108-13. — First found element of each, 111. 
— Illustrated, 261. — Galactic System added to the three which 
are illustrated, 262. 

Sun — the centre of the Solar System — its diameter, 33. — Re- 
volves on its axis — remarkable spots — how many times greater 
than the Earth — than the whole System — by usefulness and 
grandeur, the best image of his Maker, 36. 

System of the Earth, 47-52. 

System of the Heavens, 47-52. 

System of the Observer, 47-52. 

Thales, 241. 

Thermal Equator, or Equator of Heat, 196. 

Triangle of Time, 176-7-8-9. 

Tropics — accessories to the Earth's System — where drawn, 47 



298 INDEX* 

Twilight, 151. 
Tycho Brake, 253. 

Uleigh Beigh, of Samarcand, 251. 

Upper Vertex — of the artificial (terrestrial) globe — the only 

suitable place of the first Observer, 44. 
Uranography, 46. 

Venus — the Morning and Evening Star, 53. 

Vertical Circles — what they are — all belong to the Observer's 

System, and are movable, 53-4. 
ViaLactea, 27-8, 151-2. (See Galaxy.) 
Volcanoes, 195. 

Water — its great extent on the Earth's surface — necessary to the 
fertility of the land — its depth — unequal surface of the bottom 
of the Ocean, 142-& 

Winds, 197—8. — Trade-winds, 198. — Land and sea breezes, 198. 
— Calms — monsoons, 199. 

Wooden Horizon of the Terrestrial Globe, 29. 

Year — the common — the civil, 213. — The cidereal Year, 215. — 
The solar — the Year of mean solar time — the astronomical, 
217. 

Zenith — upper celestial extremity of the Observer's line, 45. 

Zenith Distance of any heavenly body, 54. 

Zones — the torrid, 114. — The frigid, 114. — The temperate, 114- 

15. — The northern temperate — historically and geographically 

the most remarkable, 117. 



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By an improved and entirely new process of manufactu- 
ring (the ball being made of a material different from that 
heretofore used, and much better for the purpose, the result 
of a long course of study and experiment), they are very 
much stronger than other Globes, and less liable to crack or 
be broken by a fall or other accident. In this respect they 
are far superior to any other Globes. 

Each Globe, (excepting the parlor pattern, which is packed 
in case3 for transportation) is put up in a neat case, with lid 
secured by a catch. The case effectually protects it from 
liability to accident and from dust : a great desideratum in 
the school-room. 

They are printed on new plates, giving the latest changes 
and divisions, including the latest Arctic and Australian dis- 
coveries, 



THE 10-INCH TERRESTRIAL GLOBE 

gives the divisions of the United States, not to be found on 
any other globe of the same size, exhibits the boundaries of 
Empires, Kingdoms, and Republics, as laid down on the latest 
maps and by the best geographers. 

As this is a new plate, we shall be able to have any new 



2 THE FRANKLIN GLOBES. 

division or discovery engraved at short notice, and feel safe 
in assuring the public that no other Globe of its size in mar- 
ket is so full and complete. 

The 10-inch Globes, parlor pattern, are mounted on ma- 
hogany frames, as represented by the cut below, and as an 
article of furniture, are an ornament to any parlor or library ; 
this style is also much approved by teachers, from its conve- 
nience in exhibiting to the scholar. They are also put up in 
beautiful Bronze Frames, which are a decided improvement 
on the old style. — Brass Quadrants of altitude accompany 
each pair of Globes. When a single Globe is ordered, an 
extra charge is made for quadrants. 




PARLOR AND HIGH-SCHOOL PATTERN. 



THE FRANKLIN GLOBES. 3 

PBICE. 

10-lnch Globe, Parlor Pattern, per pair, $32.00 

10 " " " Terrestrial 16.00 

Extra Quadrants 75 

Packing Cases for above, '. each 1.00 




TE>'-LNCH GLOBE, EROXZE FEAME. PHC€. 

10-Inch Globe, bronze frame, neat plain case, per pair, $24.00 

10 « " " " " Terrestrial, 12.00 

Extra Quadrants 75 




TEX-EN'CH GLOBE, "WOOD FRAME. Prt€€. 

10-Inch Globe, wood frame, neat plain case, per pair, $22.00 

10 " " ' " u " Terrestrial, 11.00 

Extra Quadrants 75 



THE FRANKLIN GLOBES. 



THE 6-INCH GLOBES 



give the recent changes, new States, etc., and are well suited 
to common-schools. They are put up on bronze iron frames, 
and make one of the most useful gifts that can be presented to 
a boy or girl, in these days of popular education. 




SIX-INCH GLOBE, BRONZE FRAME. 

PRICE. 

6-Inch Globe, bronze frame, neat plain case,, .per pair, $9.00 
6 " " " u " Terrestrial, 4.50 

"We commend these Globes to teachers, parents, and friends 
of education, believing that for correctness of engraving, 
strength of manufacture, beauty of finish, and lowness of 
price combined, they are unsurpassed ; and that their gen- 
eral use would greatly facilitate the acquiring of correct ideas 
of the earth's form and the relative distances of places on 
the part of the pupil, and also, the ease of teaching them on 
the part of the instructor. 



We subjoin the remarks of an influential daily paper 
(Times) on the Globe and its uses, which we commend to the 
attention of all interested in education, to the general reader, 
and to the literary of all ages and both sexes : 

GLOBE MAKING. 
M An artificial Globe is almost indispensable to the young 
scholar, for a right understanding of the very first principles 



THE FHAXEXIN GLOBES. 5 

of Geography ; yet it is surprising how little advance has 
been made in the manufacture of Globes in the last 70 years. 
A Globe now in the rooms of the Young Men's Association, 
made in 1782, in London, is the same, even to all the little 
minutia of manufacture, as those made in this country in 
1850, and no attempt seems to have been made to keep pace 
in this manufacture with the advancement of arts and sci^ 
ences in other things. 

" The attention of Messrs. Merriam, Moore & Co. was 
turned to the manufacture of Globes some two years since, 
and in examining the process of making, they became satis- 
fied that great improvements could be effected in the manu- 
facture. They accordingly commenced a course of experi- 
menting, and after an expenditure of much time and money, 
have succeeded in getting up a Globe by a new process, of 
different material from that heretofore used, and much supe- 
rior to those heretofore made. 

"A great objection to the former process was the liability 
of the Globes to crack ; this is entirely obviated by the new 
mode of making. It is not liable to break by a fall, and will 
bear the moderate blow of a hammer without being bruised 
or broken. In finish, also, as in strength, this process is very 
much superior to that heretofore used, thus combining 
strength and beauty in the article. 

" These Globes are of two sizes. A ten-inch globe, placed 
in a high ornamental frame, a beautiful article for the parlor 
or drawing-room. The same size in lower frames for the 
seminary, school, or family, packed in handsome cases for 
their safe-keeping. Also a six-inch globe, with the same du- 
rability and high finish as the former, and with a metallic 
bronze frame, an entirely new feature in the manufacture, 
making a beautiful article for the library or the parlor table. 

u We commend these Globes to our readers. At this day 
the reader of the daily news, coming as it does from every 
part of the world, needs a globe by his side, to keep in mind 
the relative position of places, and the small Globe of which 
we have spoken would make a useful as well as a beautiful 
holiday gift to a child or a family of child ren." 



6 THE FRANKLIN GLOBES. 

From the Kew York Observer. 

" "We consider these Globes as a decided and valuable im- 
provement upon the old style, which ought to be encouraged 
and patronized ; and as such we heartily commend them to 
the attention, not only of teachers, but of families and indi- 
viduals, who desire a convenient reference for geographical 
information. And so extensive is the range of current intel- 
ligence, that one needs a globe beside him to refer to the 
places mentioned in the daily newspaper." 



From S. B. Woolworth, Principal of the State Normal School, 
Albany, M. Y. 

State Nokmal School, Jan. 14, 1853. 
I have examined with considerable care a pair of ten-inch 
Globes constructed by Messrs. Merriam, Moore & Co., of 
Troy, and have been much pleased with the convenience and 
beauty of the mounting, and the apparent correctness of the 
delineations. I cheerfully recommend these Globes to the 
confidence of those who may have occasion to procure, for 
schools this indispensable aid to correct instruction in Geog- 
raphy, as among the best which I have examined. 

S. B. WOOLWORTH. 



From Thomas W. Valentine, of Albany, Redolent Editor of 
the New York Teacher. 

Messes. Mebeiam, Mooee & Co. : 

I have carefully examined your " Franklin Globes," and 
can truly say that I consider them in all respects fully equal, 
and in some points superior to any that I have ever seen. 
They combine durability with cheapness — the mechanical 
execution of them being evidently of the very first order. I 
find, moreover, that all the recent discoveries, down to the 
latest dates, are given, and that all the delineations are cor- 
rectly and faithfully made. But one of the best improve- 
ments you have made, is the means provided for their pres- 



THE FEANKLIN GLOBES. 7 

ervation. Being put in substantial cases, they are fully 
protected from the dust and accidents of the school-room — 
which an experience of many years in the use of globes, con- 
vinces me, is a very great desideratum. I would, therefore, 
cordially recommend your Globes to all teachers, confidently 
believing that wherever they shall be introduced, they will 
give the best satisfaction. Very truly yours, 

THOMAS W. VALENTINE. 



THE IMPORTANCE OF THE USE OF THE GLOBE. 

We believe the use of the Globe in teaching has been un- 
dervalued. To say nothing of its use in the higher branches 
of study, its importance as an aid in teaching Geography, 
can hardly be over-estimated. To prove this, it is only ne- 
cessary for teachers or parents to revert to their own school 
days, and ask themselves how many months or years of study 
they passed through before they acquired so correct an idea 
of the form of the earth, or the relative positions and dis- 
tances of places, as would be acquired by a single day's study 
of the Globe. For example, many scholars get the idea from 
the map that Australia and New Zealand are at the two ex- 
tremes of the earth, instead of learning that they are near 
neighbors, no farther distant than New York and Cuba ; that 
New York is much farther from England than from Liberia, 
instead of learning that it is many hundred miles nearer. 
Many other equally erroneous ideas are gained, — and these 
ideas are sometimes hardly corrected in a lifetime. The use 
of the Globe instead of the Map, or in connection with it, 
would give to the eye of the pupil correct ideas in regard to 
those things in which the map tends to mislead ; and this is 
the more important because such error once fixed in the mind, 
the impression remains there long after the understanding 
learns that it is error ; and we believe that in no way can 
the same expense be more profitably incurred for a school, 
than in the purchase of a pair of Globes of sufficient size 



8 THE FKANKLIN GLOBES. 

and fulness to be thoroughly available for the pupil in the 
study of Geography. 

Impressed with the importance of this, the publishers of 
the Franklin Globes have secured the services of Mrs. Emma 
Willard, so well known for her efficient and successful labors 
in the cause of education, to prepare a work of the following 
title : 

ASTRONOGRAPHY: 

OR 

ASTRONOMICAL GEOGRAPHY, 

FOR READING AND STUDY IN SCHOOLS, 

TAUGHT BY THE USE OF THE GLOBES. 

We invite the attention of teachers to this work. From 
the time and labor that have been spent in preparing the 
work, by Mrs. Willard, as well as from the very favorable 
opinions of eminent educationists who have examined por- 
tions of the work, it is believed that it will be found to be 
far superior to any work heretofore published on the use of 
the Globes. 






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